[Dovecot] deliver vs lda

[Daniel L. Miller]

Eduardo M KALINOWSKI wrote:
> Charles Marcus wrote:
>   
>> heh... well, they would soon enough...
>>
>> Seriously though... why call it a 'local delivery agent', when its
>> really more than that? Local suggests local/system users, and dovecot
>> delivery agent works fine for both local and virtual users. Postfix
>> calls its local delivery agent 'local', and its virtual delivery agent
>> 'virtual'
>>   
>>     
>
> It's local because it stores e-mails somewhere in the local filesystem
> hierarchy, instead of sending it to a remote machine via SMTP (or any
> other protocol).
>
> I don't know postfix a lot, but I wonder why it needs two LDAs, one for
> real users and one for virtual ones, when the only conceptual difference
> should be where to store e-mails and where to lookup information on the
> existence of the user and his mail spool directory.
>   
Postfix's "local" and "virtual" exist because of specialized lookup 
mechanisms.  Local just checks username portion of an address against 
the local password database, Virtual checks a configured mapping against 
the complete mail address.

The choice of a multi-function agent vs multiple specialized agents is a 
matter of preference and always a subject of debate.  For a Dovecot 
analogy, the current incarnation of "deliver" might be split up into 
"deliver-mbox", "deliver-maildir", and "deliver-dbox" - although that 
doesn't translate fully, as the Postfix delivery agents do both mbox & 
maildir.  I guess a better comparison would be "deliver-local", 
"deliver-ldap", "deliver-sql", etc.
-- 
Daniel