diff --git a/DMS/docker-compose.yml b/DMS/docker-compose.yml
index 78a417d..918b84f 100644
--- a/DMS/docker-compose.yml
+++ b/DMS/docker-compose.yml
@@ -135,7 +135,7 @@ services:
       - ROUNDCUBEMAIL_DB_USER=roundcube
       - ROUNDCUBEMAIL_DB_PASSWORD=${ROUNDCUBE_DB_PASSWORD}
       # Roundcube verbindet intern über den Docker-Alias
-      - ROUNDCUBEMAIL_DEFAULT_HOST=mailserver        # kein ssl:// prefix
+      - ROUNDCUBEMAIL_DEFAULT_HOST=tls://mailserver  # kein ssl:// prefix
       - ROUNDCUBEMAIL_DEFAULT_PORT=143               # IMAP ohne SSL
       - ROUNDCUBEMAIL_SMTP_SERVER=mailserver         # kein tls:// prefix  
       - ROUNDCUBEMAIL_SMTP_PORT=25                   # SMTP intern direkt