[Dovecot] Virtual Users Dovecot and Postfix

[Ben Morrow]

At  4AM +0100 on 16/02/13 you (Silvio Siefke) wrote:
> 
> i want setup my Mailserver with the Tutorial on Dovecot Wiki.
> 
> http://wiki2.dovecot.org/HowTo/VirtualUserFlatFilesPostfix
> 
> I have one question for this, must i set the Mailadresses in
> /etc/postfix/virtual too or is the passwd File from dovecot
> enough? 

The setup given in that howto will accept mail for any user at one of
the domains listed in virtual_mailbox_domains, and mail for nonexistent
users will then be bounced by Dovecot. This is a very bad idea, since
you'll end up becoming a backscatter source; you should set up a
separate Postfix table listing the valid users at those domains, and put
that table in virtual_mailbox_maps. (You don't want to use
/etc/postfix/virtual for this, you want a separate table.)

See the Postfix ADDRESS_CLASS_README.

It might instead be possible to use the facilities described in the
ADDRESS_VERIFICATION_README to verify addresses with the LMTP server
rather than consulting a preprepared list, but IMHO that approach is
wasteful and not entirely reliable.

(IMHO you should also use smtpd_restriction_classes to get the
smtpd_*_restrictions stuff out of master.cf, but that's a separate
issue.)

Ben