diff --git a/libksieve/ksieveui/util/util.cpp b/libksieve/ksieveui/util/util.cpp
--- a/libksieve/ksieveui/util/util.cpp
+++ b/libksieve/ksieveui/util/util.cpp
@@ -114,9 +114,43 @@
     } else {
         KUrl u( interface->sieveAlternateUrl() );
         const QString resultSafety = interface->safety();
+
+        if (u.protocol().isEmpty() || u.port() < 1) {
+          kWarning() << "Invalid sieve url " << u;
+          return KUrl();
+        }
+
         if ( u.protocol().toLower() == QLatin1String("sieve") && ( resultSafety ==  QLatin1String("None") ) && u.queryItem(QLatin1String("x-allow-unencrypted")).isEmpty() )
             u.addQueryItem( QLatin1String("x-allow-unencrypted"), QLatin1String("true") );
 
+        if (u.queryItem(QLatin1String("x-mech")).isEmpty()) {
+          QString authStr;
+          switch( interface->authentication() ) {
+            case MailTransport::Transport::EnumAuthenticationType::CLEAR:
+            case MailTransport::Transport::EnumAuthenticationType::PLAIN:
+              authStr = QLatin1String("PLAIN");
+              break;
+            case MailTransport::Transport::EnumAuthenticationType::LOGIN:
+              authStr = QLatin1String("LOGIN");
+              break;
+            case MailTransport::Transport::EnumAuthenticationType::CRAM_MD5:
+              authStr = QLatin1String("CRAM-MD5");
+              break;
+            case MailTransport::Transport::EnumAuthenticationType::DIGEST_MD5:
+              authStr = QLatin1String("DIGEST-MD5");
+              break;
+            case MailTransport::Transport::EnumAuthenticationType::GSSAPI:
+              authStr = QLatin1String("GSSAPI");
+              break;
+            case MailTransport::Transport::EnumAuthenticationType::ANONYMOUS:
+              authStr = QLatin1String("ANONYMOUS");
+              break;
+            default:
+              authStr = QLatin1String("PLAIN");
+              break;
+          }
+          u.addQueryItem( QLatin1String("x-mech"), authStr );
+        }
         const QString resultCustomAuthentication = interface->sieveCustomAuthentification();
         if (resultCustomAuthentication == QLatin1String("ImapUserPassword")) {
             u.setUserName( interface->userName() );
@@ -207,4 +241,4 @@
         return true;
     }
     return false;
-}
\ No newline at end of file
+}