Relay control in sendmail for roaming users

[Paul Howarth]

Bob Brennan wrote:
> I have an FC3 mailserver/webserver machine that I am trying to set up
> so that users of various web/mail domains on the machine can send and
> receive email through their preferred MUA (Outlook/Evolution/etc). The
> machine has the latest Sendmail and Dovecot running, with Squirrelmail
> supplying access to email for all domains, sending and receiving
> properly because it is on the machine itself.
> 
> The problem comes when a remote machine or webmail wants to send to
> another remote machine, say me at mydomain.com on a remote Outlook to
> me at gmail.com, which is "remote relaying". I would use the
> pop-before-smtp option that all MUAs now use for authentication.
> 
> http://www.sendmail.org/~ca/email/roaming.html#POPB4SMTP is the best
> advice I can turn up so far but it seems to be conflicting opinions
> and incomprehensible to anyone but Sendmail gurus.
> 
> Since pop-before smtp through Sendmail is very common out there -
> there must be someone who knows how to make it work step-by-step, or
> an idiot's guide on how to do it. I understand the reasons for distros
> to enable Sendmail in a mode that locks out spammers but there must be
> a secure _working_ mode as well that even a relative newbie can set up
> and still be secure(?)

My personal preference is to use SMTP AUTH rather than POP-before-SMTP, 
and to set it up on port 587 (MSA).

I don't know of a *really* good guide for setting this up, but some 
starters might be:

http://www.madboa.com/geek/sendmail-auth/
http://www.joreybump.com/code/howto/smtpauth.html
http://www.simpaticus.com/linux/sendmail-smtp-auth-howto.php

Cheers, Paul.