The Natural Philosopher wrote:
> Peter Lowrie wrote:
>> so let me get this straight. Is sendmail like a pop3 and smtp server?
>>
>> Are user accounts set up with a shell?
>>
>> The reason I ask is because I want to put this Sparcstation to use.
>> The email servers and clients are installed as a matter of course. I
>> just want to be sure it looks outwardly like a pop and smtp server.
>>
>
> No.
>
> Sendmail is a Mail Transfer Agent or MTA.
>
> It accepts incoming SMTP connections, or direct injection from other
> programs, and processes mail to deliver it to 'delivery agents' based
> on a hugely flexible rule based configurator, and it rewrites the mail
> headers on the way according to another set of rules.
> It may also reject mail in various ways.
>
> ONE of the available delivery agents is the UNIX 'mail' program which
> will deliver the mail to a file inbox - usually
> /var/spool/mail/<user>...where it may be read directly using several
> different Unix MUA's (mail USER agents) or accessed via 'popd' if this
> is set up to run, which in turn will serve incoming pop mail
> connections.

Excuse me, but the MTA does that. "mail" can read and edit that file to
delete or save individual messages: but it usually transfers saved files to
$HOMEDIR/mbox when it exits.

"mail" is an MUA, not an MTA.

> In order top set up a SPARC as a pop mail server, and an SMTP relay,
> you need:-
>
> A working internet connecting and routing

Only for external mail access, particularly for incoming mail. For
internal-only or for outgoing mail only, you can actually live with no
incoming connections.

> Working DNS name resolution

No, you can use
..
> sendmail running with the -bd switch to go into background server mode
> A correctly written sendmail.cf file. Set up to route local mail to
> the local delivery agent, and remote mail to the internet via SMTP
> User accounts for every user on the mail system. With passwords
> popd running.

No, you don't need user accounts for everyone: There are multiple ways to
have shared or even database managed user accounts that don't require local
logins and only support IMAP/POP3 access, or aliases that can transfer the
email elsewhere.

> The O'reilly book 'sendmail' has everything you need and more, and
> was, when I last did this, the definitive manual.

Agreed. I find sendmail fairly painful to configure for anything even
remotely interesting, and Postfix vastly easier to configure. Your mileage
may vary, but examples include alias management for mailman services and
running virtual servers with spam filtering, especially milters.

> Oh, and with sendmail, there are always at least 50 different ways of
> achieving the desired results, and 100 different people telling you
> their particular one is the one and only pure godlike way to set it
> up.
> Relax, just hack the bastard till it works. 99.999% of sendmail will
> never ever be needed, you can thank your lucky stars that no one now
> uses UUCP bang style path addressing..and you haven't got a bunch of
> know all academics who insist on attempting to use every address form
> known to man to prove that your configuration is not as perfect as
> their egos.*

Oh, agreed. Been there, done that, had to deal with the mortals who refused
to give NFS mounting things for Emacs RMAIL.

> Popd? - just read the man pages.

Then throw it the hell out. Proceed directly to IMAP services, preferably
with the dovecot server, and proceed to using Maildir format instead of mbox
for performance and backup reliability reasons.