[Mailman-Users] adress on same server cannot send to list with thunderbird on port 587

[Jérôme Fabre]

Hello,

I use mailman on a server that hosts all my mails for some domains. 
system is release 3 ovh based on Centos6.
with thunderbird (or any other mail client), i use port 587. But with 
this configuration, i cannot send emails to my list. I recieve an error 
message from the daemon saying "user unknown". I think postfix search a 
user in mailboxes and don't consider mailman.
If i change the port for 25 in the smtp configuration of thunderbird, 
ervery thing works fine. But i really want to use 587.
(i have a webmail on this server that can post to the lists, external 
domains can also post)

If someone knows how to fix it, thank you...