[Mailman-Users] users in multiple lists

[David LEROUX]

Hi all,

I'm a new mailman administrator, first time using it and wondering a few 
things.
First one is that we manage a bunch of lists, in which same users may be 
in different one
The result is if we send mails to, for example, three different lists 
with a common user in those lists, this user receive 3 mails, normal...
But I wonder if there's a way to make that this user receive the mail 
only once.
As I'm typing this mail, I'm thinking that it could be a postfix issue 
more than a mailman issue

Thank you for your answers, and be sure to see me again soon ;)

-- 
David Leroux