diff --git a/common/src/main/java/envoy/data/Contact.java b/common/src/main/java/envoy/data/Contact.java
index 9a5fd0a..3fe71da 100644
--- a/common/src/main/java/envoy/data/Contact.java
+++ b/common/src/main/java/envoy/data/Contact.java
@@ -17,9 +17,10 @@ import java.util.Set;
  */
 public abstract class Contact implements Serializable {
 
-	private final long								id;
-	private final transient Set<? extends Contact>	contacts;
-	private String									name;
+	protected final long								id;
+	protected final transient Set<? extends Contact>	contacts;
+
+	protected String name;
 
 	private static final long serialVersionUID = 0L;
 
@@ -55,19 +56,13 @@ public abstract class Contact implements Serializable {
 	 */
 	public void setName(String name) { this.name = name; }
 
-	/**
-	 * {@inheritDoc}
-	 */
-	@Override
-	public String toString() { return String.format("Contact[id=%d,name=%s, contacts=%s]", id, name, contacts); }
-
 	/**
 	 * Provides a hash code based on the ID of this contact.
 	 * 
 	 * @since Envoy Common v0.1-beta
 	 */
 	@Override
-	public int hashCode() { return Objects.hash(id); }
+	public final int hashCode() { return Objects.hash(id); }
 
 	/**
 	 * Tests equality to another object. If that object is a contact as well,
@@ -77,7 +72,7 @@ public abstract class Contact implements Serializable {
 	 * @return {code true} if both objects are contacts and have identical IDs
 	 */
 	@Override
-	public boolean equals(Object obj) {
+	public final boolean equals(Object obj) {
 		if (this == obj) return true;
 		if (!(obj instanceof Contact)) return false;
 		return id == ((Contact) obj).id;
diff --git a/common/src/main/java/envoy/data/Group.java b/common/src/main/java/envoy/data/Group.java
index 4eb6b02..53f816f 100644
--- a/common/src/main/java/envoy/data/Group.java
+++ b/common/src/main/java/envoy/data/Group.java
@@ -36,6 +36,9 @@ public final class Group extends Contact {
 	 */
 	public Group(long id, String name, Set<User> members) { super(id, name, members); }
 
+	@Override
+	public String toString() { return String.format("Group[id=%d,name=%s,%d member(s)]", id, name, contacts.size()); }
+
 	private void readObject(ObjectInputStream inputStream) throws Exception {
 		inputStream.defaultReadObject();
 		var contacts = Contact.class.getDeclaredField("contacts");
@@ -51,5 +54,5 @@ public final class Group extends Contact {
 
 	@SuppressWarnings("unchecked")
 	@Override
-	public Set<User> getContacts() { return (Set<User>) super.getContacts(); }
+	public Set<User> getContacts() { return (Set<User>) contacts; }
 }
diff --git a/common/src/main/java/envoy/data/User.java b/common/src/main/java/envoy/data/User.java
index 7751ce3..a423934 100644
--- a/common/src/main/java/envoy/data/User.java
+++ b/common/src/main/java/envoy/data/User.java
@@ -99,7 +99,9 @@ public final class User extends Contact {
 	}
 
 	@Override
-	public String toString() { return String.format("User[id=%d,name=%s,status=%s,contacts=%s]", getID(), getName(), status, getContacts()); }
+	public String toString() {
+		return String.format("User[id=%d,name=%s,status=%s", id, name, status) + (contacts.isEmpty() ? "]" : "," + contacts.size() + " contact(s)]");
+	}
 
 	/**
 	 * @return the current status of this user
diff --git a/server/src/main/java/envoy/server/data/Contact.java b/server/src/main/java/envoy/server/data/Contact.java
index 79cd720..43a9983 100644
--- a/server/src/main/java/envoy/server/data/Contact.java
+++ b/server/src/main/java/envoy/server/data/Contact.java
@@ -103,5 +103,5 @@ public abstract class Contact {
 	public void setCreationDate(Instant creationDate) { this.creationDate = creationDate; }
 
 	@Override
-	public String toString() { return String.format("%s[id=%d,name=%s, %d contact(s)]", getClass().getSimpleName(), id, name, contacts.size()); }
+	public String toString() { return String.format("%s[id=%d,name=%s,%d contact(s)]", getClass().getSimpleName(), id, name, contacts.size()); }
 }
diff --git a/server/src/main/java/envoy/server/data/GroupMessage.java b/server/src/main/java/envoy/server/data/GroupMessage.java
index bb96895..45be27d 100644
--- a/server/src/main/java/envoy/server/data/GroupMessage.java
+++ b/server/src/main/java/envoy/server/data/GroupMessage.java
@@ -19,10 +19,10 @@ import envoy.data.Group;
 @Entity
 @NamedQuery(
 	name = GroupMessage.getPendingGroupMsg,
-	query = "SELECT m FROM GroupMessage m JOIN m.memberMessageStatus s WHERE (KEY(s) = :userId) AND ((m.creationDate > :lastSeen)"
-			+ "OR ((m.status = envoy.data.Message$MessageStatus.RECEIVED) AND (m.receivedDate > :lastSeen))"
-			+ "OR ((m.status = envoy.data.Message$MessageStatus.READ) AND (m.readDate > :lastSeen))"
-			+ "OR ((m.lastStatusChangeDate > :lastSeen)))"
+	query = "SELECT m FROM GroupMessage m JOIN m.memberMessageStatus s WHERE KEY(s) = :userId AND (m.creationDate > :lastSeen "
+			+ "OR m.status = envoy.data.Message$MessageStatus.RECEIVED AND m.receivedDate > :lastSeen "
+			+ "OR m.status = envoy.data.Message$MessageStatus.READ AND m.readDate > :lastSeen "
+			+ "OR m.lastStatusChangeDate > :lastSeen)"
 )
 public class GroupMessage extends Message {
 
diff --git a/server/src/main/java/envoy/server/data/Message.java b/server/src/main/java/envoy/server/data/Message.java
index d99b3b0..fc564a2 100755
--- a/server/src/main/java/envoy/server/data/Message.java
+++ b/server/src/main/java/envoy/server/data/Message.java
@@ -12,11 +12,15 @@ import envoy.data.Message.MessageStatus;
 import envoy.data.MessageBuilder;
 
 /**
- * This class serves as a way to let Hibernate communicate with the server
- * without bringing the dependency of JPA/Hibernate into the client.<br>
- * It will be referenced as "database message" to clarify between the different
- * message objects.<br>
- * <br>
+ * This JPA entity, which will be referred to as database message, stores the
+ * information contained inside a {@link envoy.data.Message} inside the
+ * database, while having a slightly different data layout.
+ * <p>
+ * A message can be converted to a database message by using the
+ * {@link Message#Message(envoy.data.Message)} constructor. A database message
+ * can be converted to a regular message using the {@link Message#toCommon()}
+ * method. In both cases, the objects will not contain references to each other.
+ * <p>
  * Project: <strong>envoy-server-standalone</strong><br>
  * File: <strong>Message.java</strong><br>
  * Created: <strong>02.01.2020</strong><br>
@@ -29,9 +33,14 @@ import envoy.data.MessageBuilder;
 @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
 @NamedQuery(
 	name = Message.getPending,
-	query = "SELECT m FROM Message m WHERE (m.recipient = :user AND m.status = envoy.data.Message$MessageStatus.SENT) "
-			+ "OR (m.sender = :user) AND ((m.status = envoy.data.Message$MessageStatus.RECEIVED) AND (m.receivedDate > :lastSeen)"
-			+ "OR (m.status = envoy.data.Message$MessageStatus.READ) AND (m.readDate > :lastSeen))"
+	query = "SELECT m FROM Message m WHERE "
+			// Send to or by the user before last seen
+			+ "(m.sender = :user OR m.recipient = :user) AND m.creationDate > :lastSeen "
+			// SENT to the user
+			+ "OR m.recipient = :user AND m.status = envoy.data.Message$MessageStatus.SENT "
+			// Sent by the user and RECEIVED / READ after last seen
+			+ "OR m.sender = :user AND (m.status = envoy.data.Message$MessageStatus.RECEIVED AND m.receivedDate > :lastSeen "
+			+ "OR m.status = envoy.data.Message$MessageStatus.READ AND m.readDate > :lastSeen)"
 )
 public class Message {
 
@@ -107,17 +116,14 @@ public class Message {
 	 *         message
 	 * @since Envoy Server Standalone v0.1-alpha
 	 */
-	public envoy.data.Message toCommon() {
-		return prepareBuilder().build();
-	}
+	public envoy.data.Message toCommon() { return prepareBuilder().build(); }
 
 	/**
 	 * @return a message builder containing the state of this message
 	 * @since Envoy Server Standalone v0.1-beta
 	 */
 	MessageBuilder prepareBuilder() {
-		var builder = new MessageBuilder(sender.getID(), recipient.getID(), id).setText(
-				text)
+		var builder = new MessageBuilder(sender.getID(), recipient.getID(), id).setText(text)
 			.setCreationDate(creationDate)
 			.setReceivedDate(receivedDate)
 			.setReadDate(readDate)
diff --git a/server/src/main/java/envoy/server/processors/LoginCredentialProcessor.java b/server/src/main/java/envoy/server/processors/LoginCredentialProcessor.java
index 479e249..f7ee34e 100755
--- a/server/src/main/java/envoy/server/processors/LoginCredentialProcessor.java
+++ b/server/src/main/java/envoy/server/processors/LoginCredentialProcessor.java
@@ -123,7 +123,11 @@ public final class LoginCredentialProcessor implements ObjectProcessor<LoginCred
 
 		for (var msg : pendingMessages) {
 			final var msgCommon = msg.toCommon();
-			if (msg.getStatus() == SENT) {
+			if (msg.getCreationDate().isAfter(credentials.getLastSync())) {
+
+				// Sync without side effects
+				writeProxy.write(socketID, msgCommon);
+			} else if (msg.getStatus() == SENT) {
 
 				// Send the message
 				writeProxy.write(socketID, msgCommon);
@@ -146,34 +150,38 @@ public final class LoginCredentialProcessor implements ObjectProcessor<LoginCred
 
 			// Deliver the message to the user if he hasn't received it yet
 			if (gmsg.getMemberMessageStatus().get(user.getID()) == SENT) {
-				gmsg.getMemberMessageStatus().replace(user.getID(), RECEIVED);
+				if (gmsg.getMemberMessageStatus().replace(user.getID(), RECEIVED) != RECEIVED) {
 
-				gmsg.setLastStatusChangeDate(Instant.now());
+					gmsg.setLastStatusChangeDate(Instant.now());
 
-				writeProxy.write(socketID, gmsgCommon);
+					writeProxy.write(socketID, gmsgCommon);
 
-				// Notify all online group members about the status change
-				writeProxy.writeToOnlineContacts(gmsg.getRecipient().getContacts(),
-						new GroupMessageStatusChange(gmsg.getID(), RECEIVED, Instant
-							.now(),
-								connectionManager.getUserIDBySocketID(socketID)));
-
-				if (Collections.min(gmsg.getMemberMessageStatus().values()) == RECEIVED) {
-					gmsg.received();
-
-					// Notify online members about the status change
+					// Notify all online group members about the status change
 					writeProxy.writeToOnlineContacts(gmsg.getRecipient().getContacts(),
-							new MessageStatusChange(gmsg.getID(), gmsg.getStatus(), Instant.now()));
-				}
+							new GroupMessageStatusChange(gmsg.getID(), RECEIVED, Instant.now(), connectionManager.getUserIDBySocketID(socketID)));
 
-				PersistenceManager.getInstance().updateMessage(gmsg);
+					if (Collections.min(gmsg.getMemberMessageStatus().values()) == RECEIVED) {
+						gmsg.received();
+
+						// Notify online members about the status change
+						writeProxy.writeToOnlineContacts(gmsg.getRecipient().getContacts(),
+								new MessageStatusChange(gmsg.getID(), gmsg.getStatus(), Instant.now()));
+					}
+
+					PersistenceManager.getInstance().updateMessage(gmsg);
+				} else {
+
+					// Just send the message without updating if it was received in the past
+					writeProxy.write(socketID, gmsgCommon);
+				}
 			} else {
 
 				// Sending group message status changes
 				if (gmsg.getStatus() == SENT && gmsg.getLastStatusChangeDate().isAfter(gmsg.getCreationDate())
 						|| gmsg.getStatus() == RECEIVED && gmsg.getLastStatusChangeDate().isAfter(gmsg.getReceivedDate())) {
-					gmsg.getMemberMessageStatus().forEach((memberID, memberStatus) -> 
-					writeProxy.write(socketID, new GroupMessageStatusChange(gmsg.getID(), memberStatus, gmsg.getLastStatusChangeDate(), memberID)));
+					gmsg.getMemberMessageStatus()
+						.forEach((memberID, memberStatus) -> writeProxy.write(socketID,
+								new GroupMessageStatusChange(gmsg.getID(), memberStatus, gmsg.getLastStatusChangeDate(), memberID)));
 				}
 
 				// Deliver just a status change instead of the whole message