G DATA 365 | Mail Protection

Emails from individual senders are not delivered, even though all other emails work without any issues. What could be the reason?

If individual emails are not delivered, this may be because the inbound connector you created (as suggested in our guide) is used not only for email delivery performed by our service.

Among other things, connectors are also used, for example, to identify IP addresses and TLS certificates. This can lead to infinite loops that cause G DATA 365 | Mail Protection to no longer accept the email.

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

Solution:

If such loops occur in your environment, it is necessary to change your MX record to mailprotection.gdata.de.