Just some observations on how 10.5.4 server handles group mails and aliases:

• Mail > Settings > Mailing Lists > Enable server group … tells the server to scan all groups that have “Mailing list” enabled and update group member addresses into /etc/postfix/aliases. It uses the user record's Info > Email data. I would suggest setting the scanning to 1 min when setting things up.
• It uses /etc/postfix/aliases
• Nested groups are not expanded :(
• Users with only the Primary Group ID set to a mailinglist-enabled group will not be included in the postfix alias. Ie you should set the primary group to Staff and add all you meaningful groups as Other Groups. This looks like a bug to me…
• The teamsserver@server entry is added whenever you enable “Mailing list web archive”
• Teamsserver@server is actually delivered to /usr/share/wikid/bin/bundleMail.py
• It's now possible to handle group aliases using WGM if you don't use nested groups!