Difference btw. Dovecot Director and Dovecot Proxy

[Jiri Bourek]

On 19.7.2014 00:54, Nathan Schultheiss wrote:
> Hello,
>
> For a few days I try to understand what program (Dovecot Director or
> Dovecot Proxy) I should use for my email architecture.
> We are a hospital, and for security reasons, we must host ourselves our
> emails, and we must leave Google Apps...

OT: great, the less customers they have, the more they'll be forced to 
play nice with other mail service providers

>
> I wish to make a Dovecot backend for each department of the hospital.
> Each backend Dovecot has a local storage.
>
> Server 01: cardiology
> Server 02: emergency
> ...
> Server 05: administration
>
> Dovecot looks in the database which server to use to store email (lmtp)
> and transfer the mail for storage.
>
> I do not understand if I have to work with Dovecot Director or Proxy if
> I would that LMTP or IMAP request are forwarded to the right backend.
> Each have self storage and have not access to the other backend storage
> (no nfs, no network storage, ...).
>
> Users indicate imap.hospital.local, this point to Dovecot Director or
> Proxy and Dovecot check the login/password and forward the user to the
> right backend.
> In my database I put user at hospital = storage host 172.16.2.10 = folder
> /home/vmail/user/ (Maildir)
>
> I've read that the Director can refer the user to the same backend when
> there is a activ session (POP, IMAP, LMTP)
> But can we tell him to always refer the user to the same backend (IMAP
> and LMTP) ?
>
> I've found this picture schema who user have Dovecot Proxy => Dovecot
> Director => Dovecot Backend
> And I'm confused why they have proxy + director ?!?
>
> Can anyone tell me if I need to focus on Dovecot Director or Dovecot
> Proxy to create the architecture of this hospital ?
>
> My question is probably stupid for Dovecot sysadmin, but I'm lost in the
> WIKI :)
>
> Thanks in advance,
>
> Nathan

As for IMAP/POP3, I'd go for proxy - it's quite easy to set up if you 
have users in database, you pretty much just return 'y' as "proxy" field 
and storage backend's IP address as "host" field in password_query and 
Dovecot will do the rest.

As for LMTP - you didn't mention what MTA are you using but if it's 
Postfix, you can configure it to use database data to translate user 
name into storage IP address - then you tell it to use LMTP to deliver 
to that IP. (Not sure about other MTAs.)