Hi all,
I'm having *sudden* issues with our SMTP server (Amazon SES) erroring out while trying to send from our most active Mailman3 mailing list (~1,000 subscribers; modest Mailman3 (v 3.3.3) installation (10+ lists, Ubuntu).
Here is the message. We've got several thousand log entries like this now:
*554 Transaction failed: Duplicate header 'DKIM-Signature'* Mar 10 08:31:10 mail1 postfix/smtp[217753]: 738B53F15E: to=< brian@brianmichaelslaw.com>, relay=xxx.org[44.225.xxx.xx]:587, delay=37, delays=2/35/0.16/0.13, dsn=5.0.0, status=bounced (host said: 554 Transaction failed: Duplicate header 'DKIM-Signature'. (in reply to end of DATA command))
As we don't do any DKIM key signing on the related Postfix machine I've opened up a case with Amazon. However, if there is a troubleshooting I should adopt on this issue with regard to Postfix/Mailman I'd like to know what your recommendations are, or what steps I can follow to better help the vendor ensure that this issue isn't coming from either the Postfix machine or the Mailman machine.
Much thanks,
José Bernal Web/Application Engineer