SES blocks mail sending to t-online adresses

Question

I am receiving the following error-messages on sending to customers with t-online adresses for multiple days in a row now:

```
An error occurred while trying to deliver the mail to the following recipients:
-----@t-online.deReporting-MTA: dns; a4-13.smtp-out.eu-west-1.amazonses.com

Action: failed
Final-Recipient: rfc822; ------@t-online.de
Diagnostic-Code: smtp; 550 4.4.7 Message expired: unable to deliver in 840 minutes.<451 4.0.0 Unknown>
Status: 4.4.7
```
In the past when a IP from the shared space was blocked the message was different. This happens for all t-online Adresses. Is there a general Issue with the Provider? Any help appreciated.

Answer

New in the error this time:

```
Diagnostic-Code: smtp; 554 4.4.7 Message expired: unable to deliver in 840 minutes.<421 IP=54.240.4.11 - No more parallel connections from your address allowed>
```

Answer

We see the same issue, even with a Dedicated IP. Its only with t-online.de (and their other domains telekom.de and magenta.de). We contacted tosa@rx.t-online.de  and also the form on https://postmaster.t-online.de/kontakt.php but they rejected our request as AWS needs to get in touch with them.

SES blocks mail sending to t-online adresses

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