[sclug] Recommendations for mail server

Drew McLellan lists at allinthehead.com
Thu Jan 13 22:32:47 UTC 2005

Keith Edmunds wrote:
> On Thu, 13 Jan 2005 20:52:02 +0000
> Drew McLellan <lists at allinthehead.com> wrote:
>>I've got a box running Debian Sarge as a dedicated web server off in a 
>>datacentre somewhere. The box currently has exim installed. I need to 
>>configure a basic mail setup so a small handful of people can use POP3.
> Exim is the Debian standard, and a reasonable SMTP server. Personally I use
> Postfix on the servers I configure, but that's mostly down to personal
> preference.

Is there much configuration required at this level? When preconfiguring 
exim I answered a bunch of questions about how the server would operate 
- is that about all that's required?

>>a) POP3 boxes
>>b) SMTP relay w/ authorisation
> They're separate things. POP3 will be provided by a POP3 daemon, of which
> more in a minute, but the daemon simply serves up mail which has already
> been delivered. SMTP relaying is a function of the MTA, and Exim or Postfix
> will each do that. My personal preference is for Postfix with SASL
> authentication, which can easily be tied in to PAM authentication - in
> other words, you can create a normal user account on the server for a user,
> and they can use that username/password to authenticate with Postfix to
> send mail

On the basis that a recommendation is better than a default setting, it 
sounds like I should take a close look at Postfix. The above scenario 
sounds good to me.

>>and ideally:
>>c) web interface for account maintenance (webmin's ok)
>>d) work with a standard webmail tool like squirrelmail.
> If you need a web interface then I'd recommend webmin. Squirrelmail - an
> excellent application - reads from an IMAP server, so your earlier
> requirement of POP3 is in conflict here, probably. If possible, I'd
> recommend IMAP because all mail is then kept on the server, meaning that
> there is only one location to backup. It IS possible to access mailboxes
> by both POP3 and IMAP, but you should be SURE you want to do that before
> going ahead.

Looks like I picked a bad example in squirrelmail. I didn't realise it 
was IMAP. Being familiar with the basic operational differences between 
IMAP and POP3, it's POP3 I need in this case.

> The IMAP server I'd recommend is Dovecot; it also includes a POP3 daemon.

Would Dovecot be a good choice for POP3 only? Or would something else 
suit better?

>>I guess the main problem I have is understanding which tool does what. I 
>>guess an MTA like exim will route mail in and out of the box, but does 
>>that leave me needing something else to handle the accounts? Or do I 
>>create system accounts? What about POP3? and all those sorts of dumb 
> You can have a "virtual" mail server that doesn't need a system account for
> each mailbox, but unless you have a huge number of mailboxes this is
> probably overkill. Roles: the MTA does indeed route mail in and out of the
> box as you say. Incoming mail is passed to a Mail Delivery Agent (MDA),
> which may be part of the MTA or separate from it. The MDA delivers the mail
> in a given format, typically mbox or Maildir, to each user. A POP3 server
> will read each user's mail and deliver it to their local mailbox, typically
> part of their Mail User Agent (MUA), such as Outlook/Thunderbird/etc.
> Usually POP3 then deletes the mail from the server. An IMAP server also
> serves up mail to the MUA, but this time the mail remains on the server.

So in a basic set up, every mail user would have a system account. 
Incoming mail would be routed to that account's mailbox by the MTA 
(Postfix or Exim).

Sat on top of that is a POP3 server. This delves into the system 
mailboxes and delivers the mail the user, upon the user requesting it.

Sending mail requires the user to authenticate with the MTA, which then 
accepts the mail and forwards it for delivery.

Have I got that right?

> Does that help at all? Or has it spawned 254 new questions?

That helps *massively* Keith, thank you.


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