[TUHS] Who is running their own mail server and what do you run?
gtaylor at tnetconsulting.net
Fri Sep 22 07:02:53 AEST 2017
On 09/21/2017 02:05 PM, Norman Wilson wrote:
> I run my own mail server, on systems in my basement.
> It is a setup that no one in their right mind would
Maybe ... maybe not.
I think a number of TUHS subscribers enjoy special configurations.
> but the details may actually be proper for this list.
I'm only replying to the historical aspects.
> A firewall/gateway system runs a custom SMTP server,
> which can do simple filtering based on the SMTP envelope,
> SMTP commands, calling IP address and hostname. It is
> also able to call external commands to pass judgement on
> a caller or a particular message.
> If mail is accepted, it is passed through a simple
> MTA and a stupidly-simple queueing setup (the latter
> made of shell scripts) to be sent via SMTP to a
> different internal system, which uses the same SMTP
> server and MTA to deliver to local mailboxes.
> Outbound mail is more or less the obvious inverse.
> I have put off naming names for dramatic effect. The
> two systems in question are MicroVAX IIIs running
> my somewhat-hacked-up version of post-10/e Research
> UNIX. The MTA is early-1990s-vintage upas. The SMTP
> server, SMTP sender, and queuing stuff are my own.
IMHO the dramatic effect was warranted. (I was thinking that it's not
too complex up until you said MicroVAZ III.)
It sounds to me like your MTA is completely separate from the SMTP
stack. - Would I be correct in guessing that your SMTP stack reads
from and writes to ""queues that look like mailboxes to your MTA?
By the way, what you've done sounds very impressive, and likely challenging.
> I wrote the SMTP server originally not long after I left
> Bell Labs; I was now in a world where sendmail was the
> least-troublesome MTA, but in those days every month
> brought news of a new sendmail vulnerability, so I wrote
> my own simple server to act as a condom.
I doubt that many of todays script kiddies would do such a thing. I
> Over time it
> grew a bit, as I became interested in problems like
> what sorts of breakin attempts are there in real life
> (back then one received occasional DEBUG or WIZ commands,
> but I haven't seen any since the turn of the century);
> what sorts of simple filtering at the SMTP level will
> get rid of most junk mail. The code is more complicated
> than it used to be, but is still small enough that I am
> reasonably confident that it is safe to expose to the
> The SMTP sender and the queueing scripts came later,
> when I decided to host my own mail. Both were designed
> in too much of a hurry.
So, what was SMTP used for before you hosted your own email? Was it a
minimal implementation to get logs / outgoing messages off of the box?
> There is no official spam filtering (no bogofilter or
> the like). A few simple rules that really just enforce
> aspects of the SMTP standard seem to catch most junk
> callers: HELO argument must contain at least one . (standard
> says it must be your FQDN) and must not be *.* (I see dozens
> of those every day!); sender must not speak until my server
> has issued a complete greeting (I follow Wietse Venema in
> this: send a line with a continuation marker first, then
> sleep five seconds or so, then send a finish). I also
> have a very simple, naive greylisting implementation that
> wouldn't work well for a site with lots of users, but is
> fine for my personal traffic. The greylisting is implemented
> with a pair of external shell scripts.
> I have had it in mind for a long time to consult the Spamhaus
> XBL too. It would be easy enough to do with another plug-in
> shell script. There are stupid reasons having to do with my
> current DNS setup that make that impractical for now.
> The mail setup works, but is showing its age, as is the
> use of Research UNIX and such old, slow hardware as a network
> gateway. One of these years, when I have the time, I'd like
> first to redo the mail setup so that mailboxes are stored
> on my central file server (a Sun X2200 running Solaris 10,
> or perhaps something illumos-based by the time I actually
> do all this); then set up a new gateway, probably based on
> OpenBSD. Perhaps I should calculate how much hardware I
> could buy from the power savings of turning off just one of
> the two MicroVAXes for a year.
Could you keep your working configuration and save power by migrating
your configuration to emulation? Perhaps on a Raspberry Pi or the likes.
> I have yet to see an MTA that is spare enough for my taste,
> but the old upas code just doesn't quite do what I want any
> more, and is too messy to port around. (Pursuant to the
> conversation earlier here about autoconf: these days I try
> to need no configuration magic at all, which works as long
> as I stick to ISO C and POSIX and am careful about networking.
> upas was written in messier days.) At the moment I'm leaning
> toward qmail, just because for other reasons I'm familiar with
> it, though for my personal use I will want to make a few changes
> here and there. But I'll want to keep my SMTP server because
> I am still interested in what goes on there.
> Norman Wilson
> Toronto ON
Grant. . . .
unix || die
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