Issues delivering mail from GMX to my postfix

[Carsten Strotmann (sys4)]

Hi,

I've got a report from a user that tries to send an mail from GMX to my
private mail account.

The mail-account is secured by DANE/TLSA and running on Postfix.
"dane.sys4.de" does not report any issues, but GMX refuses to deliver
mail with this message:

----------------------------schnipp----------------------------
This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of
its recipients. This is a permanent error. The following address(es)
failed:

cas at strotmann.de:
remote MX does not support STARTTLS
----------------------------schnipp----------------------------

Has anyone seen a similar issue? Any ideas how to troubleshoot?

Best regards

Carsten

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