Quoting Timo Sirainen tss@iki.fi:
On Tue, 2011-08-23 at 19:27 +0100, a.smith@ukgrid.net wrote:
In my test, actually what I have is a vmail user with primary group vmail and secondary group mailnull. Which as mentioned results in this error:
It doesn't actually matter what groups you have assigned to vmail user. Dovecot only enables the primary group (and not even that if you've overridden it in config), and apparently Exim does the same too.
The supplementary groups don't automatically get enabled when process's UID switched, it requires explicit extra code to do it. In most installations this is just useless extra work and a potential accidental security hole.
Ok, I assumed that secondary groups are honoured in almost all
instances on a UNIX or Linux platform. I can add a note to the wiki
making it explicit that the group must be the primary group if you
think it's appropriate...