Enable group mailing list in Server.app not working

Question

Hello everyone,
I have been trying to enable a new (?) feature of Server.app : "Enable group mailing list". Until now, it does not work for me. When I try to send an email to the group [email protected], Mail tells me that the smtp server cannot send my message. Here is what I see on the server's /var/log/mail.log file :
Sep 10 16:55:54 testserver01.pretendco.net postfix/smtpd[2311]: NOQUEUE: reject: RCPT from testclient01.pretendco.net[10.1.101.10]: 550 5.1.1 <[email protected]>: Recipient address rejected: User unknown in local recipient table; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<testclient01.pretendco.net>
Sep 10 16:55:54 testserver01.pretendco.net postfix/smtpd[2311]: disconnect from testclient01.pretendco.net[10.1.101.10]
It is interesting to note that group mailing list aren't even mentioned in the Mac OS X Server Advanced Administration Guide :
http://help.apple.com/advancedserveradmin/mac/10.8/#apd9430d30c-5796-4a20-a8f9-1 20638938942
Does any has any good/bad experience with group mailing lists under Mountain Lion Server ? Any advice ?
Thanks a lot !

Answer 1

Hello Mark23 and thanks for your help !
The log says nothing particular when I (un)set the "Enable Group Mailing List Option". The only difference I see is a line saying mail_groups[127]: sleeping for: 1 hour(s). I have no idea what this means exactly. Googling it did not help me much either.
I post the /etc/aliases file below. Interesting : every time I (un)set the "Enable Group Mailing List" option, the /etc/aliases last access time changes. But the md5 hash of the file stays the same.
I guess that the "sudo newaliases" uses /etc/aliases to construct the binary database file /etc/aliases.db ? It seems that this script is run every time I (un)check the option since the access time of *both* /etc/aliases and /etc/aliases.db are changed to the current time.
Do you have any other option checked ?
Here is my /etc/aliases (I removed the blocks of comments at the beginning and at the end):
# Person who should get root's mail. Don't receive mail as root!
#root:                    you
# Basic system aliases -- these MUST be present
MAILER-DAEMON:          postmaster
postmaster:          root
# General redirections for pseudo accounts
bin:                    root
daemon:                    root
named:                    root
nobody:                    root
uucp:                    root
www:                    root
ftp-bugs:          root
postfix:          root
# Put your local aliases here.
# ==== Begin auto-generated section ========================================
# This section of the aliases file is auto-generated by server admin tools
# Please do not edit this section or your modifications will be lost
# === End auto-generated section ===========================================
# Well-known aliases
manager:          root
dumper:                    root
operator:          root
abuse:                    postmaster
# trap decode to catch security attacks
decode:                    root