diff --git a/client/src/main/java/envoy/client/data/Chat.java b/client/src/main/java/envoy/client/data/Chat.java
index 80b2a97..ba40bbe 100644
--- a/client/src/main/java/envoy/client/data/Chat.java
+++ b/client/src/main/java/envoy/client/data/Chat.java
@@ -27,6 +27,8 @@ public class Chat implements Serializable {
 
 	protected int unreadAmount;
 
+	private boolean disabled;
+
 	/**
 	 * Stores the last time an {@link envoy.event.IsTyping} event has been sent.
 	 */
@@ -168,4 +170,22 @@ public class Chat implements Serializable {
 	 * @since Envoy Client v0.2-beta
 	 */
 	public void lastWritingEventWasNow() { lastWritingEvent = System.currentTimeMillis(); }
+
+	/**
+	 * Determines whether messages can be sent in this chat. Should be true i.e. for
+	 * chats whose recipient deleted this client as a contact.
+	 *
+	 * @return whether this {@code Chat} has been disabled
+	 * @since Envoy Client v0.3-beta
+	 */
+	public boolean isDisabled() { return disabled; }
+
+	/**
+	 * Determines whether messages can be sent in this chat. Should be true i.e. for
+	 * chats whose recipient deleted this client as a contact.
+	 *
+	 * @param disabled the disabled to set
+	 * @since Envoy Client v0.3-beta
+	 */
+	public void setDisabled(boolean disabled) { this.disabled = disabled; }
 }
diff --git a/client/src/main/java/envoy/client/data/GroupChat.java b/client/src/main/java/envoy/client/data/GroupChat.java
index 188709c..049c32e 100644
--- a/client/src/main/java/envoy/client/data/GroupChat.java
+++ b/client/src/main/java/envoy/client/data/GroupChat.java
@@ -25,7 +25,7 @@ public final class GroupChat extends Chat {
 	 * @param recipient the group whose members receive the messages
 	 * @since Envoy Client v0.1-beta
 	 */
-	public GroupChat(User sender, Contact recipient) {
+	public GroupChat(User sender, Group recipient) {
 		super(recipient);
 		this.sender = sender;
 	}
diff --git a/client/src/main/java/envoy/client/data/LocalDB.java b/client/src/main/java/envoy/client/data/LocalDB.java
index 13db9df..691a878 100644
--- a/client/src/main/java/envoy/client/data/LocalDB.java
+++ b/client/src/main/java/envoy/client/data/LocalDB.java
@@ -14,6 +14,7 @@ import envoy.client.event.*;
 import envoy.data.*;
 import envoy.data.Message.MessageStatus;
 import envoy.event.*;
+import envoy.event.contact.*;
 import envoy.exception.EnvoyException;
 import envoy.util.*;
 
@@ -34,11 +35,12 @@ public final class LocalDB implements EventListener {
 
 	// Data
 	private User					user;
-	private Map<String, User>		users		= Collections.synchronizedMap(new HashMap<>());
-	private ObservableList<Chat>	chats		= FXCollections.observableArrayList();
+	private Map<String, User>		users				= Collections.synchronizedMap(new HashMap<>());
+	private ObservableList<Chat>	chats				= FXCollections.observableArrayList();
 	private IDGenerator				idGenerator;
-	private CacheMap				cacheMap	= new CacheMap();
+	private CacheMap				cacheMap			= new CacheMap();
 	private String					authToken;
+	private Set<? extends Contact>	originalContacts	= Set.of();
 
 	// Auto save timer
 	private Timer	autoSaver;
@@ -163,7 +165,7 @@ public final class LocalDB implements EventListener {
 		user.getContacts()
 			.stream()
 			.filter(c -> !c.equals(user) && getChat(c.getID()).isEmpty())
-			.map(c -> c instanceof User ? new Chat(c) : new GroupChat(user, c))
+			.map(c -> c instanceof User ? new Chat(c) : new GroupChat(user, (Group) c))
 			.forEach(chats::add);
 	}
 
@@ -197,7 +199,7 @@ public final class LocalDB implements EventListener {
 	 */
 	@Event(eventType = EnvoyCloseEvent.class, priority = 1000)
 	private synchronized void save() {
-		EnvoyLog.getLogger(LocalDB.class).log(Level.INFO, "Saving local database...");
+		EnvoyLog.getLogger(LocalDB.class).log(Level.FINER, "Saving local database...");
 
 		// Save users
 		try {
@@ -240,6 +242,31 @@ public final class LocalDB implements EventListener {
 		getChat(evt.getID()).map(Chat::getRecipient).map(User.class::cast).ifPresent(u -> u.setStatus(evt.get()));
 	}
 
+	@Event(priority = 200)
+	private void onUserOperation(UserOperation operation) {
+		final var eventUser = operation.get();
+		switch (operation.getOperationType()) {
+			case ADD:
+				getUsers().put(eventUser.getName(), eventUser);
+				Platform.runLater(() -> chats.add(0, new Chat(eventUser)));
+				break;
+			case REMOVE:
+				getChat(eventUser.getID()).ifPresent(chat -> chat.setDisabled(true));
+				break;
+		}
+	}
+
+	@Event
+	private void onGroupCreationResult(GroupCreationResult evt) {
+		final var newGroup = evt.get();
+
+		// The group creation was not successful
+		if (newGroup == null) return;
+
+		// The group was successfully created
+		else Platform.runLater(() -> chats.add(new GroupChat(user, newGroup)));
+	}
+
 	@Event(priority = 150)
 	private void onGroupResize(GroupResize evt) { getChat(evt.getGroupID()).map(Chat::getRecipient).map(Group.class::cast).ifPresent(evt::apply); }
 
@@ -296,6 +323,9 @@ public final class LocalDB implements EventListener {
 	@Event(priority = 500)
 	private void onOwnStatusChange(OwnStatusChange statusChange) { user.setStatus(statusChange.get()); }
 
+	@Event(eventType = ContactsChangedSinceLastLogin.class, priority = 500)
+	private void onContactsChangedSinceLastLogin() { if (user != null) originalContacts = user.getContacts(); }
+
 	/**
 	 * @return a {@code Map<String, User>} of all users stored locally with their
 	 *         user names as keys
@@ -323,6 +353,25 @@ public final class LocalDB implements EventListener {
 	 */
 	public Optional<Chat> getChat(long recipientID) { return chats.stream().filter(c -> c.getRecipient().getID() == recipientID).findAny(); }
 
+	/**
+	 * Sets the given user as base of this {@code LocalDB}.
+	 * Additionally compares his contacts with the ones returned by the server, in
+	 * case they might have been deleted.
+	 *
+	 * @param user the user to set
+	 * @since Envoy Client v0.2-alpha
+	 */
+	public void setUserAndMergeContacts(User user) {
+		this.user = user;
+		if (originalContacts.isEmpty()) return;
+		else {
+
+			// mark all chats of deleted contacts
+			originalContacts.removeAll(user.getContacts());
+			originalContacts.forEach(contact -> getChat(contact.getID()).ifPresent(chat -> chat.setDisabled(true)));
+		}
+	}
+
 	/**
 	 * @return all saved {@link Chat} objects that list the client user as the
 	 *         sender
diff --git a/client/src/main/java/envoy/client/net/Client.java b/client/src/main/java/envoy/client/net/Client.java
index 0db43ef..e84388d 100644
--- a/client/src/main/java/envoy/client/net/Client.java
+++ b/client/src/main/java/envoy/client/net/Client.java
@@ -9,6 +9,7 @@ import envoy.client.data.*;
 import envoy.client.event.EnvoyCloseEvent;
 import envoy.data.*;
 import envoy.event.*;
+import envoy.event.contact.ContactsChangedSinceLastLogin;
 import envoy.util.*;
 
 import dev.kske.eventbus.*;
@@ -29,6 +30,7 @@ public final class Client implements EventListener, Closeable {
 	private Socket		socket;
 	private Receiver	receiver;
 	private boolean		online;
+	private boolean		isHandShake;
 
 	// Asynchronously initialized during handshake
 	private volatile User		sender;
@@ -61,6 +63,7 @@ public final class Client implements EventListener, Closeable {
 	 */
 	public void performHandshake(LoginCredentials credentials, CacheMap cacheMap) throws TimeoutException, IOException, InterruptedException {
 		if (online) throw new IllegalStateException("Handshake has already been performed successfully");
+		isHandShake = true;
 
 		// Establish TCP connection
 		logger.log(Level.FINER, String.format("Attempting connection to server %s:%d...", config.getServer(), config.getPort()));
@@ -92,14 +95,19 @@ public final class Client implements EventListener, Closeable {
 			if (rejected) {
 				socket.close();
 				receiver.removeAllProcessors();
+				isHandShake = false;
 				return;
 			}
 
-			if (System.currentTimeMillis() - start > 5000) throw new TimeoutException("Did not log in after 5 seconds");
+			if (System.currentTimeMillis() - start > 5000) {
+				isHandShake = false;
+				throw new TimeoutException("Did not log in after 5 seconds");
+			}
 			Thread.sleep(500);
 		}
 
-		online = true;
+		online		= true;
+		isHandShake	= false;
 		logger.log(Level.INFO, "Handshake completed.");
 	}
 
@@ -146,7 +154,7 @@ public final class Client implements EventListener, Closeable {
 		logger.log(Level.FINE, "Sending " + obj);
 		try {
 			SerializationUtils.writeBytesWithLength(obj, socket.getOutputStream());
-		} catch (IOException e) {
+		} catch (final IOException e) {
 			throw new RuntimeException(e);
 		}
 	}
@@ -174,7 +182,20 @@ public final class Client implements EventListener, Closeable {
 	}
 
 	@Event(eventType = HandshakeRejection.class, priority = 1000)
-	private void onHandshakeRejection() { rejected = true; }
+	private void onHandshakeRejection() {
+		rejected	= true;
+		isHandShake	= false;
+	}
+
+	@Event(eventType = ContactsChangedSinceLastLogin.class, priority = 1000)
+	private void onContactsChangedSinceLastLogin() {
+		if (!isHandShake) {
+			logger.log(Level.WARNING, "Received a request to check contacts while not in the handshake");
+
+			// TODO: consume event once event consumption is implemented
+			return;
+		}
+	}
 
 	@Override
 	@Event(eventType = EnvoyCloseEvent.class, priority = 800)
diff --git a/client/src/main/java/envoy/client/ui/Startup.java b/client/src/main/java/envoy/client/ui/Startup.java
index a93bf81..cd4ddbc 100644
--- a/client/src/main/java/envoy/client/ui/Startup.java
+++ b/client/src/main/java/envoy/client/ui/Startup.java
@@ -179,7 +179,7 @@ public final class Startup extends Application {
 
 		// Set client user in local database
 		final var user = client.getSender();
-		localDB.setUser(user);
+		localDB.setUserAndMergeContacts(user);
 
 		// Initialize chats in local database
 		try {
diff --git a/client/src/main/java/envoy/client/ui/control/ChatControl.java b/client/src/main/java/envoy/client/ui/control/ChatControl.java
index 353bdaf..6d4b535 100644
--- a/client/src/main/java/envoy/client/ui/control/ChatControl.java
+++ b/client/src/main/java/envoy/client/ui/control/ChatControl.java
@@ -59,6 +59,8 @@ public final class ChatControl extends HBox {
 			vbox.getChildren().add(unreadMessagesLabel);
 			getChildren().add(vbox);
 		}
-		getStyleClass().add("list-element");
+
+		// Set background depending on whether it is disabled or not
+		getStyleClass().add(chat.isDisabled() ? "disabled-chat" : "list-element");
 	}
 }
diff --git a/client/src/main/java/envoy/client/ui/controller/ChatScene.java b/client/src/main/java/envoy/client/ui/controller/ChatScene.java
index 4103a5b..4c98c76 100644
--- a/client/src/main/java/envoy/client/ui/controller/ChatScene.java
+++ b/client/src/main/java/envoy/client/ui/controller/ChatScene.java
@@ -37,7 +37,7 @@ import envoy.data.*;
 import envoy.data.Attachment.AttachmentType;
 import envoy.data.Message.MessageStatus;
 import envoy.event.*;
-import envoy.event.contact.ContactOperation;
+import envoy.event.contact.UserOperation;
 import envoy.exception.EnvoyException;
 import envoy.util.EnvoyLog;
 
@@ -270,18 +270,22 @@ public final class ChatScene implements EventListener, Restorable {
 	}
 
 	@Event
-	private void onContactOperation(ContactOperation operation) {
-		final var contact = operation.get();
-		switch (operation.getOperationType()) {
-			case ADD:
-				if (contact instanceof User) localDB.getUsers().put(contact.getName(), (User) contact);
-				final var chat = contact instanceof User ? new Chat(contact) : new GroupChat(client.getSender(), contact);
-				Platform.runLater(() -> ((ObservableList<Chat>) chats.getSource()).add(0, chat));
-				break;
-			case REMOVE:
-				Platform.runLater(() -> chats.getSource().removeIf(c -> c.getRecipient().equals(contact)));
-				break;
-		}
+	private void onUserOperation(UserOperation operation) {
+		// All ADD dependant logic resides in LocalDB
+		if (operation.getOperationType().equals(ElementOperation.REMOVE))
+			if (currentChat != null && currentChat.getRecipient().equals(operation.get())) Platform.runLater(this::resetState);
+	}
+
+	@Event
+	private void onGroupResize(GroupResize resize) {
+		final var chatFound = localDB.getChat(resize.getGroupID());
+		Platform.runLater(() -> {
+			chatList.refresh();
+
+			// Update the top-bar status label if all conditions apply
+			if (currentChat != null && currentChat.getRecipient().equals(chatFound.get().getRecipient()))
+				chatFound.ifPresent(chat -> topBarStatusLabel.setText(chat.getRecipient().getContacts().size() + " members"));
+		});
 	}
 
 	@Event(eventType = NoAttachments.class)
@@ -297,8 +301,8 @@ public final class ChatScene implements EventListener, Restorable {
 		});
 	}
 
-	@Event
-	private void onGroupCreationResult(GroupCreationResult result) { Platform.runLater(() -> newGroupButton.setDisable(!result.get())); }
+	@Event(priority = 150)
+	private void onGroupCreationResult(GroupCreationResult result) { Platform.runLater(() -> newGroupButton.setDisable(result.get() == null)); }
 
 	@Event(eventType = ThemeChangeEvent.class)
 	private void onThemeChange() {
@@ -311,7 +315,6 @@ public final class ChatScene implements EventListener, Restorable {
 		clientProfilePic.setImage(IconUtil.loadIconThemeSensitive("user_icon", 43));
 		chatList.setCellFactory(new ListCellFactory<>(ChatControl::new));
 		messageList.setCellFactory(MessageListCell::new);
-		// TODO: cache image
 		if (currentChat != null)
 			if (currentChat.getRecipient() instanceof User) recipientProfilePic.setImage(IconUtil.loadIconThemeSensitive("user_icon", 43));
 			else recipientProfilePic.setImage(IconUtil.loadIconThemeSensitive("group_icon", 43));
@@ -330,9 +333,11 @@ public final class ChatScene implements EventListener, Restorable {
 	 */
 	@FXML
 	private void chatListClicked() {
-		if (chatList.getSelectionModel().isEmpty()) return;
+		if (currentChat != null && chatList.getSelectionModel().isEmpty()) return;
+		final var chat = chatList.getSelectionModel().getSelectedItem();
+		if (chat == null) return;
 
-		final var user = chatList.getSelectionModel().getSelectedItem().getRecipient();
+		final var user = chat.getRecipient();
 		if (user != null && (currentChat == null || !user.equals(currentChat.getRecipient()))) {
 
 			// LEON: JFC <===> JAVA FRIED CHICKEN <=/=> Java Foundation Classes
@@ -362,17 +367,24 @@ public final class ChatScene implements EventListener, Restorable {
 			remainingChars
 				.setText(String.format("remaining chars: %d/%d", MAX_MESSAGE_LENGTH - messageTextArea.getText().length(), MAX_MESSAGE_LENGTH));
 		}
-		messageTextArea.setDisable(currentChat == null || postingPermanentlyDisabled);
-		voiceButton.setDisable(!recorder.isSupported());
-		attachmentButton.setDisable(false);
+
+		// Enable or disable the necessary UI controls
+		final var chatEditable = currentChat == null || currentChat.isDisabled();
+		messageTextArea.setDisable(chatEditable || postingPermanentlyDisabled);
+		voiceButton.setDisable(!recorder.isSupported() || chatEditable);
+		attachmentButton.setDisable(chatEditable);
 		chatList.refresh();
 
+		// Design the top bar
 		if (currentChat != null) {
 			topBarContactLabel.setText(currentChat.getRecipient().getName());
+			topBarContactLabel.setVisible(true);
 			if (currentChat.getRecipient() instanceof User) {
 				final var status = ((User) currentChat.getRecipient()).getStatus().toString();
 				topBarStatusLabel.setText(status);
+				topBarStatusLabel.getStyleClass().clear();
 				topBarStatusLabel.getStyleClass().add(status.toLowerCase());
+				topBarStatusLabel.setVisible(true);
 				recipientProfilePic.setImage(IconUtil.loadIconThemeSensitive("user_icon", 43));
 			} else {
 				topBarStatusLabel.setText(currentChat.getRecipient().getContacts().size() + " members");
@@ -385,8 +397,11 @@ public final class ChatScene implements EventListener, Restorable {
 			clip.setArcHeight(43);
 			clip.setArcWidth(43);
 			recipientProfilePic.setClip(clip);
-
+			messageList.getStyleClass().clear();
 			messageSearchButton.setVisible(true);
+
+			// Change the background of the message list if the chat is disabled
+			if (currentChat.isDisabled()) messageList.getStyleClass().add("disabled-chat");
 		}
 	}
 
@@ -664,9 +679,9 @@ public final class ChatScene implements EventListener, Restorable {
 			Platform.runLater(() -> {
 				chats.getSource().remove(currentChat);
 				((ObservableList<Chat>) chats.getSource()).add(0, currentChat);
-				chatList.getSelectionModel().select(0);
 				localDB.getChats().remove(currentChat);
 				localDB.getChats().add(0, currentChat);
+				chatList.getSelectionModel().select(0);
 			});
 			scrollToMessageListEnd();
 
@@ -711,7 +726,8 @@ public final class ChatScene implements EventListener, Restorable {
 	 * @since Envoy Client v0.1-beta
 	 */
 	private void updateAttachmentView(boolean visible) {
-		if (!attachmentView.getImage().equals(DEFAULT_ATTACHMENT_VIEW_IMAGE)) attachmentView.setImage(DEFAULT_ATTACHMENT_VIEW_IMAGE);
+		if (!(attachmentView.getImage() == null || attachmentView.getImage().equals(DEFAULT_ATTACHMENT_VIEW_IMAGE)))
+			attachmentView.setImage(DEFAULT_ATTACHMENT_VIEW_IMAGE);
 		attachmentView.setVisible(visible);
 	}
 
@@ -734,7 +750,62 @@ public final class ChatScene implements EventListener, Restorable {
 	// Context menu actions
 
 	@FXML
-	private void deleteContact() { try {} catch (final NullPointerException e) {} }
+	private void blockOrDeleteContact() {
+		final var selectedChat = chatList.getSelectionModel().getSelectedItem();
+
+		if (selectedChat == null) return;
+		// If a contact has already been blocked deletes this chat else only blocks him
+		if (selectedChat.isDisabled()) UserUtil.deleteContact(selectedChat.getRecipient());
+		else UserUtil.blockContact(selectedChat.getRecipient());
+	}
+
+	/**
+	 * Redesigns the UI when the {@link Chat} of the given contact has been marked
+	 * as disabled.
+	 *
+	 * @param recipient       the contact whose chat got disabled
+	 * @param refreshChatList whether to refresh the chatList
+	 * @since Envoy Client v0.3-beta
+	 */
+	public void disableChat(Contact recipient, boolean refreshChatList) {
+		if (refreshChatList) chatList.refresh();
+		if (currentChat != null && currentChat.getRecipient().equals(recipient)) {
+			messageTextArea.setDisable(true);
+			voiceButton.setDisable(true);
+			attachmentButton.setDisable(true);
+			pendingAttachment = null;
+			messageList.getStyleClass().clear();
+			messageList.getStyleClass().add("disabled-chat");
+		}
+	}
+
+	/**
+	 * Resets every component back to its inital state before a chat was selected.
+	 *
+	 * @since Envoy Client v0.3-beta
+	 */
+	public void resetState() {
+		currentChat = null;
+		chatList.getSelectionModel().clearSelection();
+		messageList.getItems().clear();
+		messageTextArea.setDisable(true);
+		attachmentView.setImage(null);
+		topBarContactLabel.setVisible(false);
+		topBarStatusLabel.setVisible(false);
+		messageSearchButton.setVisible(false);
+		messageTextArea.clear();
+		messageTextArea.setDisable(true);
+		attachmentButton.setDisable(true);
+		voiceButton.setDisable(true);
+		remainingChars.setVisible(false);
+		pendingAttachment = null;
+		recipientProfilePic.setImage(null);
+
+		// It is a valid case that cancel can cause a NullPointerException
+		try {
+			recorder.cancel();
+		} catch (final NullPointerException e) {}
+	}
 
 	@FXML
 	private void copyAndPostMessage() {
diff --git a/client/src/main/java/envoy/client/ui/controller/ContactSearchTab.java b/client/src/main/java/envoy/client/ui/controller/ContactSearchTab.java
index b573345..380c549 100644
--- a/client/src/main/java/envoy/client/ui/controller/ContactSearchTab.java
+++ b/client/src/main/java/envoy/client/ui/controller/ContactSearchTab.java
@@ -63,7 +63,7 @@ public class ContactSearchTab implements EventListener {
 	}
 
 	@Event
-	private void onContactOperation(ContactOperation operation) {
+	private void onUserOperation(UserOperation operation) {
 		final var contact = operation.get();
 		if (operation.getOperationType() == ElementOperation.ADD) Platform.runLater(() -> {
 			userList.getItems().remove(contact);
@@ -96,7 +96,7 @@ public class ContactSearchTab implements EventListener {
 	}
 
 	/**
-	 * Sends an {@link ContactOperation} for the selected user to the
+	 * Sends an {@link UserOperation} for the selected user to the
 	 * server.
 	 *
 	 * @since Envoy Client v0.1-beta
@@ -114,7 +114,7 @@ public class ContactSearchTab implements EventListener {
 	private void addAsContact() {
 
 		// Sends the event to the server
-		final var event = new ContactOperation(currentlySelectedUser, ElementOperation.ADD);
+		final var event = new UserOperation(currentlySelectedUser, ElementOperation.ADD);
 		client.send(event);
 
 		// Removes the chosen user and updates the UI
diff --git a/client/src/main/java/envoy/client/ui/controller/GroupCreationTab.java b/client/src/main/java/envoy/client/ui/controller/GroupCreationTab.java
index 23ec485..d262214 100644
--- a/client/src/main/java/envoy/client/ui/controller/GroupCreationTab.java
+++ b/client/src/main/java/envoy/client/ui/controller/GroupCreationTab.java
@@ -16,7 +16,7 @@ import envoy.client.ui.control.*;
 import envoy.client.ui.listcell.ListCellFactory;
 import envoy.data.*;
 import envoy.event.GroupCreation;
-import envoy.event.contact.ContactOperation;
+import envoy.event.contact.UserOperation;
 import envoy.util.Bounds;
 
 import dev.kske.eventbus.*;
@@ -234,8 +234,8 @@ public class GroupCreationTab implements EventListener {
 	}
 
 	@Event
-	private void onContactOperation(ContactOperation operation) {
-		if (operation.get() instanceof User) Platform.runLater(() -> {
+	private void onUserOperation(UserOperation operation) {
+		Platform.runLater(() -> {
 			switch (operation.getOperationType()) {
 				case ADD:
 					userList.getItems().add((User) operation.get());
diff --git a/client/src/main/java/envoy/client/util/UserUtil.java b/client/src/main/java/envoy/client/util/UserUtil.java
index 4f1b37b..dc34455 100644
--- a/client/src/main/java/envoy/client/util/UserUtil.java
+++ b/client/src/main/java/envoy/client/util/UserUtil.java
@@ -5,12 +5,15 @@ import java.util.logging.Level;
 import javafx.scene.control.Alert;
 import javafx.scene.control.Alert.AlertType;
 
-import envoy.client.data.Context;
+import envoy.client.data.*;
 import envoy.client.event.*;
 import envoy.client.helper.*;
 import envoy.client.ui.SceneContext.SceneInfo;
+import envoy.client.ui.controller.ChatScene;
+import envoy.data.*;
 import envoy.data.User.UserStatus;
-import envoy.event.UserStatusChange;
+import envoy.event.*;
+import envoy.event.contact.UserOperation;
 import envoy.util.EnvoyLog;
 
 import dev.kske.eventbus.EventBus;
@@ -23,6 +26,8 @@ import dev.kske.eventbus.EventBus;
  */
 public final class UserUtil {
 
+	private static final Context context = Context.getInstance();
+
 	private UserUtil() {}
 
 	/**
@@ -40,7 +45,7 @@ public final class UserUtil {
 			EnvoyLog.getLogger(ShutdownHelper.class).log(Level.INFO, "A logout was requested");
 			EventBus.getInstance().dispatch(new EnvoyCloseEvent());
 			EventBus.getInstance().dispatch(new Logout());
-			Context.getInstance().getSceneContext().load(SceneInfo.LOGIN_SCENE);
+			context.getSceneContext().load(SceneInfo.LOGIN_SCENE);
 		});
 	}
 
@@ -54,11 +59,56 @@ public final class UserUtil {
 	public static void changeStatus(UserStatus newStatus) {
 
 		// Sending the already active status is a valid action
-		if (newStatus.equals(Context.getInstance().getLocalDB().getUser().getStatus())) return;
+		if (newStatus.equals(context.getLocalDB().getUser().getStatus())) return;
 		else {
 			EventBus.getInstance().dispatch(new OwnStatusChange(newStatus));
-			if (Context.getInstance().getClient().isOnline())
-				Context.getInstance().getClient().send(new UserStatusChange(Context.getInstance().getLocalDB().getUser().getID(), newStatus));
+			if (context.getClient().isOnline()) context.getClient().send(new UserStatusChange(context.getLocalDB().getUser().getID(), newStatus));
+		}
+	}
+
+	/**
+	 * Removes the given contact. Should not be confused with the method that is
+	 * called when the server reports that a contact has been deleted while the user
+	 * was offline.
+	 *
+	 * @param block the contact that should be removed
+	 * @since Envoy Client v0.3-beta
+	 * @see LocalDB#setUserAndMergeContacts(envoy.data.User)
+	 */
+	public static void blockContact(Contact block) {
+		if (!context.getClient().isOnline() || block == null) return;
+		else {
+			final var alert = new Alert(AlertType.CONFIRMATION);
+			alert.setContentText("Are you sure you want to block " + block.getName() + "?");
+			AlertHelper.confirmAction(alert, () -> {
+				context.getClient()
+					.send(block instanceof User ? new UserOperation((User) block, ElementOperation.REMOVE)
+							: new GroupResize(context.getLocalDB().getUser(), (Group) block, ElementOperation.REMOVE));
+				context.getLocalDB().getChat(block.getID()).ifPresent(chat -> chat.setDisabled(true));
+				final var controller = context.getSceneContext().getController();
+				if (controller instanceof ChatScene) ((ChatScene) controller).disableChat(block, true);
+			});
+		}
+	}
+
+	/**
+	 * Deletes the given contact with all his messages entirely.
+	 *
+	 * @param delete the contact to delete
+	 * @since Envoy Client v0.3-beta
+	 */
+	public static void deleteContact(Contact delete) {
+		if (!context.getClient().isOnline() || delete == null) return;
+		else {
+			final var alert = new Alert(AlertType.CONFIRMATION);
+			alert.setContentText("Are you sure you want to delete " + delete.getName()
+					+ " entirely? All messages with this contact will be deleted. This action cannot be undone.");
+			AlertHelper.confirmAction(alert, () -> {
+				context.getLocalDB().getUsers().remove(delete.getName());
+				context.getLocalDB().getChats().removeIf(chat -> chat.getRecipient().equals(delete));
+				if (context.getSceneContext().getController() instanceof ChatScene)
+					((ChatScene) context.getSceneContext().getController()).resetState();
+			});
 		}
 	}
 }
diff --git a/client/src/main/resources/css/base.css b/client/src/main/resources/css/base.css
index 28d276c..bfe4da2 100644
--- a/client/src/main/resources/css/base.css
+++ b/client/src/main/resources/css/base.css
@@ -139,20 +139,25 @@
 
 .tab-pane {
     -fx-tab-max-height: 0.0 ;
-} 
+}
+
 .tab-pane .tab-header-area {
     visibility: hidden ;
     -fx-padding: -20.0 0.0 0.0 0.0;
 }
 
+.disabled-chat {
+	-fx-background-color: #F04000;
+}
+
 #quick-select-list .scroll-bar:horizontal{
-	-fx-pref-height: 0;
-	-fx-max-height: 0;
-	-fx-min-height: 0; 
+	-fx-pref-height: 0.0;
+	-fx-max-height: 0.0;
+	-fx-min-height: 0.0; 
 }
 
 #quick-select-list .scroll-bar:vertical{
-	-fx-pref-width: 0;
-	-fx-max-width: 0;
-	-fx-min-width: 0; 
+	-fx-pref-width: 0.0;
+	-fx-max-width: 0.0;
+	-fx-min-width: 0.0; 
 }
diff --git a/client/src/main/resources/fxml/ChatScene.fxml b/client/src/main/resources/fxml/ChatScene.fxml
index 8221f19..8368e4b 100644
--- a/client/src/main/resources/fxml/ChatScene.fxml
+++ b/client/src/main/resources/fxml/ChatScene.fxml
@@ -130,7 +130,7 @@
 												<ContextMenu anchorLocation="CONTENT_TOP_LEFT">
 													<items>
 														<MenuItem fx:id="deleteContactMenuItem"
-															mnemonicParsing="false" onAction="#deleteContact"
+															mnemonicParsing="false" onAction="#blockOrDeleteContact"
 															text="Delete" />
 													</items>
 												</ContextMenu>
diff --git a/common/src/main/java/envoy/event/GroupCreation.java b/common/src/main/java/envoy/event/GroupCreation.java
index 02270ee..ffd7851 100644
--- a/common/src/main/java/envoy/event/GroupCreation.java
+++ b/common/src/main/java/envoy/event/GroupCreation.java
@@ -17,14 +17,14 @@ public final class GroupCreation extends Event<String> {
 	private static final long serialVersionUID = 0L;
 
 	/**
-	 * @param value            the name of this group at creation time
+	 * @param name             the name of this group at creation time
 	 * @param initialMemberIDs the IDs of all {@link User}s that should be group
 	 *                         members from the beginning on (excluding the creator
 	 *                         of this group)
 	 * @since Envoy Common v0.1-beta
 	 */
-	public GroupCreation(String value, Set<Long> initialMemberIDs) {
-		super(value);
+	public GroupCreation(String name, Set<Long> initialMemberIDs) {
+		super(name);
 		this.initialMemberIDs = initialMemberIDs != null ? initialMemberIDs : new HashSet<>();
 	}
 
diff --git a/common/src/main/java/envoy/event/GroupCreationResult.java b/common/src/main/java/envoy/event/GroupCreationResult.java
index 3944ec2..14ae2f6 100644
--- a/common/src/main/java/envoy/event/GroupCreationResult.java
+++ b/common/src/main/java/envoy/event/GroupCreationResult.java
@@ -1,5 +1,7 @@
 package envoy.event;
 
+import envoy.data.Group;
+
 /**
  * Used to communicate with a client that his request to create a group might
  * have been rejected as it might be disabled on his current server.
@@ -7,15 +9,23 @@ package envoy.event;
  * @author Leon Hofmeister
  * @since Envoy Common v0.2-beta
  */
-public class GroupCreationResult extends Event<Boolean> {
+public class GroupCreationResult extends Event<Group> {
 
 	private static final long serialVersionUID = 1L;
 
 	/**
-	 * Creates a new {@code GroupCreationResult}.
+	 * Creates a new {@code GroupCreationResult} that implies the failure of this
+	 * {@link GroupCreationResult}.
 	 *
-	 * @param success whether the GroupCreation sent before was successful
 	 * @since Envoy Common v0.2-beta
 	 */
-	public GroupCreationResult(boolean success) { super(success); }
+	public GroupCreationResult() { super(null); }
+
+	/**
+	 * Creates a new {@code GroupCreationResult}.
+	 *
+	 * @param resultGroup the group the server created
+	 * @since Envoy Common v0.2-beta
+	 */
+	public GroupCreationResult(Group resultGroup) { super(resultGroup); }
 }
diff --git a/common/src/main/java/envoy/event/GroupResize.java b/common/src/main/java/envoy/event/GroupResize.java
index c8e8c76..4df5f97 100644
--- a/common/src/main/java/envoy/event/GroupResize.java
+++ b/common/src/main/java/envoy/event/GroupResize.java
@@ -33,13 +33,12 @@ public final class GroupResize extends Event<User> {
 	 */
 	public GroupResize(User user, Group group, ElementOperation operation) {
 		super(user);
-		this.operation	= operation;
-		if (group.getContacts().contains(user)) {
-			if (operation.equals(ADD))
-				throw new IllegalArgumentException(String.format("Cannot add %s to %s!", user, group));
-		} else if (operation.equals(REMOVE))
-			throw new IllegalArgumentException(String.format("Cannot remove %s from %s!", user, group));
-		groupID	= group.getID();
+		this.operation = operation;
+		final var contained = group.getContacts().contains(user);
+		if (contained && operation.equals(ADD))
+			throw new IllegalArgumentException(String.format("Cannot add %s to %s!", user, group));
+		else if (operation.equals(REMOVE) && !contained) throw new IllegalArgumentException(String.format("Cannot remove %s from %s!", user, group));
+		groupID = group.getID();
 	}
 
 	/**
@@ -72,5 +71,5 @@ public final class GroupResize extends Event<User> {
 	}
 
 	@Override
-	public String toString() { return String.format("GroupResize[userid=%d,groupid=%d,operation=%s]", get(), groupID, operation); }
+	public String toString() { return String.format("GroupResize[user=%s,groupid=%d,operation=%s]", get(), groupID, operation); }
 }
diff --git a/common/src/main/java/envoy/event/contact/ContactDeletionSinceLastLogin.java b/common/src/main/java/envoy/event/contact/ContactsChangedSinceLastLogin.java
similarity index 82%
rename from common/src/main/java/envoy/event/contact/ContactDeletionSinceLastLogin.java
rename to common/src/main/java/envoy/event/contact/ContactsChangedSinceLastLogin.java
index cda2483..f8734e8 100644
--- a/common/src/main/java/envoy/event/contact/ContactDeletionSinceLastLogin.java
+++ b/common/src/main/java/envoy/event/contact/ContactsChangedSinceLastLogin.java
@@ -9,7 +9,7 @@ import envoy.event.Event.Valueless;
  * @author Leon Hofmeister
  * @since Envoy Common v0.3-beta
  */
-public class ContactDeletionSinceLastLogin extends Valueless {
+public class ContactsChangedSinceLastLogin extends Valueless {
 
 	private static final long serialVersionUID = 1L;
 }
diff --git a/common/src/main/java/envoy/event/contact/ContactOperation.java b/common/src/main/java/envoy/event/contact/UserOperation.java
similarity index 56%
rename from common/src/main/java/envoy/event/contact/ContactOperation.java
rename to common/src/main/java/envoy/event/contact/UserOperation.java
index a31d147..666183e 100644
--- a/common/src/main/java/envoy/event/contact/ContactOperation.java
+++ b/common/src/main/java/envoy/event/contact/UserOperation.java
@@ -1,35 +1,38 @@
 package envoy.event.contact;
 
-import envoy.data.Contact;
+import envoy.data.User;
 import envoy.event.*;
 
 /**
  * Signifies the modification of a contact list.
  *
  * @author Maximilian K&auml;fer
- * @since Envoy Common v0.2-alpha
+ * @since Envoy Common v0.3-beta
  */
-public final class ContactOperation extends Event<Contact> {
+public final class UserOperation extends Event<User> {
 
 	private final ElementOperation operationType;
 
 	private static final long serialVersionUID = 1L;
 
 	/**
-	 * Initializes a {@link ContactOperation}.
+	 * Initializes a {@link UserOperation}.
 	 *
 	 * @param contact       the user on which the operation is performed
 	 * @param operationType the type of operation to perform
-	 * @since Envoy Common v0.2-alpha
+	 * @since Envoy Common v0.3-beta
 	 */
-	public ContactOperation(Contact contact, ElementOperation operationType) {
+	public UserOperation(User contact, ElementOperation operationType) {
 		super(contact);
 		this.operationType = operationType;
 	}
 
 	/**
 	 * @return the type of operation to perform
-	 * @since Envoy Common v0.2-alpha
+	 * @since Envoy Common v0.3-beta
 	 */
 	public ElementOperation getOperationType() { return operationType; }
+
+	@Override
+	public String toString() { return String.format("%s[contact=%s, operation=%s]", UserOperation.class.getSimpleName(), value, operationType); }
 }
diff --git a/server/src/main/java/envoy/server/processors/ContactOperationProcessor.java b/server/src/main/java/envoy/server/processors/ContactOperationProcessor.java
index 8049ed6..1fa74fb 100755
--- a/server/src/main/java/envoy/server/processors/ContactOperationProcessor.java
+++ b/server/src/main/java/envoy/server/processors/ContactOperationProcessor.java
@@ -4,7 +4,7 @@ import java.time.Instant;
 import java.util.logging.*;
 
 import envoy.event.ElementOperation;
-import envoy.event.contact.ContactOperation;
+import envoy.event.contact.UserOperation;
 import envoy.server.data.*;
 import envoy.server.net.*;
 import envoy.util.EnvoyLog;
@@ -13,14 +13,14 @@ import envoy.util.EnvoyLog;
  * @author Kai S. K. Engelbart
  * @since Envoy Server Standalone v0.1-alpha
  */
-public final class ContactOperationProcessor implements ObjectProcessor<ContactOperation> {
+public final class ContactOperationProcessor implements ObjectProcessor<UserOperation> {
 
 	private static final ConnectionManager	connectionManager	= ConnectionManager.getInstance();
 	private static final Logger				logger				= EnvoyLog.getLogger(ContactOperationProcessor.class);
 	private static final PersistenceManager	persistenceManager	= PersistenceManager.getInstance();
 
 	@Override
-	public void process(ContactOperation evt, long socketId, ObjectWriteProxy writeProxy) {
+	public void process(UserOperation evt, long socketId, ObjectWriteProxy writeProxy) {
 		final long	userID		= ConnectionManager.getInstance().getUserIDBySocketID(socketId);
 		final long	contactID	= evt.get().getID();
 		final var	sender		= persistenceManager.getUserByID(userID);
@@ -31,7 +31,7 @@ public final class ContactOperationProcessor implements ObjectProcessor<ContactO
 
 				// Notify the contact if online
 				if (connectionManager.isOnline(contactID))
-					writeProxy.write(connectionManager.getSocketID(contactID), new ContactOperation(sender.toCommon(), ElementOperation.ADD));
+					writeProxy.write(connectionManager.getSocketID(contactID), new UserOperation(sender.toCommon(), ElementOperation.ADD));
 				break;
 			case REMOVE:
 
@@ -49,7 +49,7 @@ public final class ContactOperationProcessor implements ObjectProcessor<ContactO
 
 					// Notify the removed contact if online
 					if (connectionManager.isOnline(contactID))
-						writeProxy.write(connectionManager.getSocketID(contactID), new ContactOperation(sender.toCommon(), ElementOperation.REMOVE));
+						writeProxy.write(connectionManager.getSocketID(contactID), new UserOperation(sender.toCommon(), ElementOperation.REMOVE));
 				} else {
 
 					// The sender wants to be removed from a Group
@@ -60,7 +60,7 @@ public final class ContactOperationProcessor implements ObjectProcessor<ContactO
 					else {
 
 						// Informing the other members
-						writeProxy.writeToOnlineContacts(group.getContacts(), new ContactOperation(sender.toCommon(), ElementOperation.REMOVE));
+						writeProxy.writeToOnlineContacts(group.getContacts(), new UserOperation(sender.toCommon(), ElementOperation.REMOVE));
 						group.getContacts().forEach(c -> ((User) c).setLatestContactDeletion(Instant.now()));
 					}
 				}
diff --git a/server/src/main/java/envoy/server/processors/GroupCreationProcessor.java b/server/src/main/java/envoy/server/processors/GroupCreationProcessor.java
index 8f40af2..3540238 100644
--- a/server/src/main/java/envoy/server/processors/GroupCreationProcessor.java
+++ b/server/src/main/java/envoy/server/processors/GroupCreationProcessor.java
@@ -5,7 +5,6 @@ import static envoy.server.Startup.config;
 import java.util.HashSet;
 
 import envoy.event.*;
-import envoy.event.contact.ContactOperation;
 import envoy.server.data.*;
 import envoy.server.net.*;
 
@@ -21,8 +20,10 @@ public final class GroupCreationProcessor implements ObjectProcessor<GroupCreati
 	@Override
 	public void process(GroupCreation groupCreation, long socketID, ObjectWriteProxy writeProxy) {
 		// Don't allow the creation of groups if manually disabled
-		writeProxy.write(socketID, new GroupCreationResult(config.isGroupSupportEnabled()));
-		if (!config.isGroupSupportEnabled()) return;
+		if (!config.isGroupSupportEnabled()) {
+			writeProxy.write(socketID, new GroupCreationResult());
+			return;
+		}
 		final envoy.server.data.Group group = new envoy.server.data.Group();
 		group.setName(groupCreation.get());
 		group.setContacts(new HashSet<>());
@@ -31,11 +32,13 @@ public final class GroupCreationProcessor implements ObjectProcessor<GroupCreati
 		group.getContacts().forEach(c -> c.getContacts().add(group));
 		group.getContacts().add(persistenceManager.getUserByID(connectionManager.getUserIDBySocketID(socketID)));
 		persistenceManager.addContact(group);
+		final var resultGroup = group.toCommon();
 		group.getContacts()
 			.stream()
 			.map(Contact::getID)
 			.filter(connectionManager::isOnline)
 			.map(connectionManager::getSocketID)
-			.forEach(memberSocketID -> writeProxy.write(memberSocketID, new ContactOperation(group.toCommon(), ElementOperation.ADD)));
+			.forEach(memberSocketID -> writeProxy.write(memberSocketID, new GroupCreationResult(resultGroup)));
+		writeProxy.write(socketID, new GroupCreationResult(resultGroup));
 	}
 }
diff --git a/server/src/main/java/envoy/server/processors/LoginCredentialProcessor.java b/server/src/main/java/envoy/server/processors/LoginCredentialProcessor.java
index 2526de3..ba484db 100755
--- a/server/src/main/java/envoy/server/processors/LoginCredentialProcessor.java
+++ b/server/src/main/java/envoy/server/processors/LoginCredentialProcessor.java
@@ -13,7 +13,7 @@ import javax.persistence.NoResultException;
 
 import envoy.data.LoginCredentials;
 import envoy.event.*;
-import envoy.event.contact.ContactDeletionSinceLastLogin;
+import envoy.event.contact.ContactsChangedSinceLastLogin;
 import envoy.server.data.*;
 import envoy.server.net.*;
 import envoy.server.util.*;
@@ -207,11 +207,10 @@ public final class LoginCredentialProcessor implements ObjectProcessor<LoginCred
 					writeProxy.write(socketID, new MessageStatusChange(gmsgCommon));
 			}
 		}
+		// Notify the user if a contact deletion has happened since he last logged in
+		if (user.getLatestContactDeletion().isAfter(user.getLastSeen())) writeProxy.write(socketID, new ContactsChangedSinceLastLogin());
 
 		// Complete the handshake
 		writeProxy.write(socketID, user.toCommon());
-
-		// Notify the user if a contact deletion has happened since he last logged in
-		if (user.getLatestContactDeletion().isAfter(user.getLastSeen())) writeProxy.write(socketID, new ContactDeletionSinceLastLogin());
 	}
 }