G DATA Mail Protection

Emails from certain senders do not arrive, although all other emails work without issues. What could be causing this?

If certain emails do not arrive, this may be because the inbound connector you created (as suggested in our instructions) is also being used for purposes other than email delivery by us.

Connectors are also used to identify IP addresses and TLS certificates, for example. This can result in repeated email-routing loops that cause G DATA Mail Protection to stop accepting the email.

This behavior has been reported to us in cases where the sender’s server uses the DMARC specification, among other scenarios.

Solution:

If you encounter these loops, you must change your MX record to mailprotection.gdata.de.