I’ve been putting off moving my mail system to the new server for a few weeks now since the old system was configured from scratch using the original config files and not the debian style config files. The differences in the Exim config are extreme. Debian splits the one large config file into lots of smaller files. This is great if: you never worked with exim before, you aren’t trying to migrate an existing configuration that is in one large file, and you don’t have all kinds of custom stuff like imap, spamassassin, greylisting mixed in. Yeah, not me. Even though I find the “one large file” a whole lot faster and easier to read, the Debian way has one big advantage: it is way easier for external scripts and packages to drop their custom config into exim. They just add a file to the right directory and thats it.

So I decided to go for it and merge my custom stuff into the Debain config. Greylisting worked out-of-the-box, spamassassin needed some minor tweaks, exim was (more or less) easy. The p.i.t.a. with exim is when you know exactly what is missing and where it would be configured, but because of “smart debian scripts” you have to find some config in an unrelated script and put the value there so it gets put in the right placeholder.

Here is a little summary in case I ever do this again and need to see if I forgot something:
– cyrus: copy /var/spool/cyrus/mail/ , /var/lib/cyrus/user/ , use cyradm to add the user.blargh account and /usr/sbin/cyrreconstruct -rf user (don’t forget the sieve filters)
– getmail: nothing special here, just copy config and add cronjob
– spamassassin: alter exim acl to set noscan for auth’d connections and have spamassassin scan everything not “noscan” (because per default local mail isn’t scanned, that includes everything we pick up via getmail)
– exim: check update-exim4.conf.conf for stupid entries, remember to turn on TLS (imap can use the same certificates), since we are using sasl for imap, have smtp auth use the same database (plain_saslauthd_server), turn on TLS by creating a file conf.d/main/00_exim4-config_localmacros with “MAIN_TLS_ENABLE = true” in it

Now that I’m done I found a pretty detailed German website with steps to set up such a system E-Mail-Server mit Debian, Exim und Cyrus. I did the exim router/transports a bit differently to have a bit more control over what goes where when. Still, defiantly worth reading if you are thinking about building such a system.