Le lun. 9 sept. 2019 à 12:08, Francis <francisd@gmail.com> a écrit :

Hello,

I migrated our mail infrastructure to Dovecot on Ubuntu 18.04 some months ago. It works fine, but recently some users told me that they sometime receive duplicated emails. Same email content, same headers including message-id.

I'm using two dovecot servers on two sites. Both server are in cluster. We don't use shared folders. All users that reported this issue so far are using the same server instance. The problematic emails are coming from local users on that instance too. The examples they given to me was emails with many recipients (To/CC). A specific message can be received twice (or more) by recipient A but only once by recipient B. I didn't see anything in the logs about sieve rules that redirect emails to others recipients.

Where should I look to diagnostic this issue?

Hello,

Thanks for your hints. The message from Битус Павел in another thread today seem to be similar to my problem. I asked my users if the affected messages are processed by a local rules in Thunderbird and they said yes. I asked them to replaces theirs local rules by sieve rules instead. We'll see if it fixes the problem.

Thanks!

--
Francis