I run my own mail server, on systems in my basement. It is a setup that no one in their right mind would replicate, but the details may actually be proper for this list. 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. 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. 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 network. 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. 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. 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