Improved error message

app/src/main/java/eu/faircode/email/ConnectionHelper.java

@@ -496,6 +496,19 @@ public class ConnectionHelper {
         return false;
     }
 
+    static boolean isAborted(Throwable ex) {
+        while (ex != null) {
+            String msg = ex.getMessage();
+            if (msg != null &&
+                    (msg.contains("Connection reset by peer") ||
+                            msg.contains("Connection closed by peer")))
+                return true;
+            ex = ex.getCause();
+        }
+
+        return false;
+    }
+
     static boolean isMaxConnections(Throwable ex) {
         while (ex != null) {
             if (isMaxConnections(ex.getMessage()))

app/src/main/java/eu/faircode/email/EmailService.java

@@ -37,6 +37,7 @@ import androidx.annotation.NonNull;
 import androidx.preference.PreferenceManager;
 
 import com.sun.mail.gimap.GmailSSLProvider;
+import com.sun.mail.iap.ConnectionException;
 import com.sun.mail.iap.ProtocolException;
 import com.sun.mail.imap.IMAPFolder;
 import com.sun.mail.imap.IMAPStore;
@@ -592,6 +593,9 @@ public class EmailService implements AutoCloseable {
             if (ex.getMessage() != null && ex.getMessage().contains("Command Error. 10"))
                 throw new AuthenticationFailedException(context.getString(R.string.title_service_error10), ex);
 
+            if (ConnectionHelper.isAborted(ex))
+                throw new MessagingException("The server or network actively aborted the connection", ex);
+
             if (purpose == PURPOSE_CHECK) {
                 if (port == 995 && !("pop3".equals(protocol) || "pop3s".equals(protocol)))
                     throw new MessagingException(context.getString(R.string.title_service_port), ex);