real duplicates of some e-mails / dovecot-2.3.19

Hi,

we have the issue, that some(!) e-mails we receive are duplicated when processed by dovecot and stored to the users inbox.

The mails are binary identical, same message ID, same size etc. diff sees no difference ….

For now we only see that it happens do small mails max. +- 5k in size.

And in dose not happen for all mails, but some are spam, some are internal mails some are newsletter which are expected…. and it happens for different users.

Dose anyone have/had a similar issue?

Any suggestion or idea would be helpful. Thanks . Götz