The end of Dovecot Director?

[Amol Kulkarni]

Nginx has an mail proxy for pop, imap, smtp.
Can it be used instead of director ?

On Fri, 21 Oct 2022 at 16:21, <hi at zakaria.website> wrote:

> On 2022-10-21 10:51, Zhang Huangbin wrote:
> >> On Oct 21, 2022, at 5:23 PM, hi at zakaria.website wrote:
> >>
> >> I was wondering if one can achieve the same implementation with
> >> haproxy without dovecot director?
> >
> > The most important part of Director is it makes sure same mail user
> > always proxied to same backend IMAP server.
> >
> > If mailbox is in Maildir format (and stored on shared storage like
> > NFS), accessing it from different server may corrupt Dovecot index
> > files and mailbox becomes unaccessible. Director perfectly avoids this
> > issue.
> >
> > HAProxy can proxy mail user from same client IP to same backend IMAP
> > server, but not same mail user from different IPs.
> >
> > Quote (https://doc.dovecot.org/admin_manual/director/dovecotdirector/):
> >
> > "Director can be used by Dovecot’s IMAP/POP3/LMTP proxy to keep a
> > temporary user -> mail server mapping. As long as user has simultaneous
> > connections, the user is always redirected to the same server. Each
> > proxy server is running its own director process, and the directors are
> > communicating the state to each others. Directors are mainly useful for
> > setups where all of the mail storage is seen by all servers, such as
> > with NFS or a cluster filesystem."
> >
> > ----
> > Zhang Huangbin, founder of:
> > - iRedMail: Open source email server solution:
> > https://www.iredmail.org/
> > - Spider: Lightweight, on-premises Email Archiving Software:
> > https://spiderd.io
>
> Aha makes sense, although I was not able to see how can index files be
> corrupted when its if will going to be updated, its in same manner as
> from different connection, e.g. opening email account from different app
> clients, with different connections, does not corrupt the index files?
>
> Also, Is it the issue Director resolving as well its with maintaining
> the logged in dovecot connection to same backend? Anyhow, thanks for
> your valuable efforts in clearing this :)
>
> I wondered if there is any other solution to avoid corrupting index
> files? Perhaps if dovecot offer database indexing as well as login
> sessions, it seems that this would eliminate Director requirement, and
> offer better high availability, as for now userdb/authdb is only
> available per my knowledge, and using database cluster resolves the
> issue with user and auth queries during simultaneous connections to a
> different backends.
>
> Otherwise, it seems in large enterprise deployment with high
> availability a Director implementation will be needed, hopefully we will
> find an alternative solution by the time Dovecot 3 is released.
>
> I might need to get my head around building dovecot with customised
> modules and review the code which was removed and return it back, if
> anyone is planning to this, and well off ahead of me, please let me
> know, we might be able to help one another.
>
> With thanks.
>
> Zakaria.
>
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