[Dovecot] Postfix LDA vs the Dovecot LDA + other quetions

[Timo Sirainen]

On Feb 23, 2009, at 9:35 PM, Linux Advocate wrote:

>> I just heard that Postfix doesn't allow you to do that (as you  
>> would have
>> noticed too). So just use vmail.
>
> Ok. but its amazing that dovecot can deliver as vmail, a user who  
> doesnt exist.....how does it accomplish this?

Huh? Maybe you're confusing some concepts. Let's see..

vmail = UNIX user = typically in /etc/passwd. Postfix's pipe program  
looks up the UID number based on the UNIX username. Typically from / 
etc/passwd. Then it sets the deliver process's UNIX UID to this number.

Dovecot deliver then reads the config file and looks up the  
destination username from dovecot-auth. Depending on your  
configuration, it either receives vmail (which gets converted to UID)  
or the UID number directly. In any case it notices that the process's  
current UNIX UID is the same as the looked up UID, so it does nothing.

Destination username lookup is completely different from the UNIX UID,  
so there's no need to have a "vmail" user listed in Dovecot's passdb/ 
userdb. It's never looked up from there.

> [root at fwgw vmail]# ls -l
>
> drwx------ 6 postfix postfix 4096 Feb 23 18:25 mesara.biz
>
> Do i need to changes the permissions on the above?

Yes. Otherwise you'll get a permission denied error.

You could always just try and see what error messages Dovecot logs.  
It's really good at giving understandable error messages, especially  
the latest v1.1 version.