[Dovecot] BUG - lmtp multiple recipients fail - setuid issue?

[Timo Sirainen]

On Mon, 2011-08-01 at 14:28 -0700, Boris Lordis wrote:
> Jul 27 11:24:42 testmailserver dovecot: lmtp(12412, steve): Error:
> link(/spool/mail/j/jerry/mail/INBOX/u.20423,
> /spool/mail/s/steve/mail/INBOX/.temp.1311791081.P12412Q2M989550.testmailserver.)
> failed: Permission denied

It shouldn't even try this.. I guess both INBOX directories use the same
group? That's why Dovecot's internal check fails to realize that it
can't use link().

This is now fixed in v2.1 hg tree. Too big of a change to fix in v2.0.
You could work around it by using unique GIDs for users, or patching
Dovecot's source code (mail_storage_copy_can_use_hardlink() to always
return FALSE)