[Dovecot] ACL Groups

[Daniel L. Miller]

From the wiki:

ACL groups support works by returning a comma-separated acl_groups extra 
field <http://wiki2.dovecot.org/UserDatabase/ExtraFields> from userdb, 
which contains all the groups the user belongs to. User's UNIX groups 
have no effect on ACLs (you can "enable" them by using a special 
post-login script <http://wiki2.dovecot.org/PostLoginScripting>).


I've read that over several times - I still don't understand that.  Are 
"ACL Groups" defined and managed by Dovecot - and described somewhere 
else in the docs - or are they UNIX groups that previously had no affect 
on mail access but by being listed in the "acl_groups" field they now 
have relevance?
--
Daniel