Scott James Remnant

EGBB 131607Z 140024 19014KT 9999 BKN025
TEMPO 0002 7000 -RA BKN010
BECMG 0811 26015KT
PROB30 TEMPO 0919 26015G25KT 7000 -SHRA

A thirty percent probability of light showers tomorrow, with cloud base at 2,500ft.

As my nan used to say, it’s got two chances…

Like most geeks, I run my own mail server. The burden of administering it is much less than the increased flexibility in filtering incoming mail, let alone dealing with SPAM.

My mail server configuration has remained pretty static the entire time, and controversially, I’ve always used qmail.

The reason for this dates back to my first sysadmin job in the mid-to-late nineties, and the decision in those days did tend to be sendmail or qmail; with the security conscious choosing the latter.

qmail’s delivery system is a little odd, everything on the left hand side up to the first “-” is considered a user, and everything after can be used for filtering.

The default local delivery component takes this into account, so e-mail to scott-foo can be filtered by the /home/scott/.qmail-foo file.

This gives a pretty natural way to deal with mailing lists; you subscribe with a unique address for that list, and all the mail goes into the right folder automatically.

This has served me reasonably well over the years, with heavy patching across the daemon to add features such as LDAP integration, and SPAM filtering that I wanted.

Unfortunately it’s been getting to burdensome to maintain. Since it’s not true open source software, and is effectively abandoned upstream, it’s not as up to date as I’d like.

SPAM filtering tends to take place in the local delivery loop, rather than at SMTP time; and due to the strange delivery system, it’s unreasonably hard to perform any kind of sender verification or greylisting.

Since every special address is filtered differently, it’s quite hard to add common filtering unless it’s pre-planned and you use addresses with a common prefix.

The clincher has been dealing with super-sites like Launchpad which send huge amounts of different e-mails to a single address, and no facility to separate that from your published contact address.

I needed a better mail server.

So I’ve now moved to exim.

I was surprised by how quickly I was able to pick it up, I did the migration in two day outages. The first to simply migrate delivery and stash the mail in one big folder, and the second to customise the delivery and filtering to my liking.

I’ve also re-subscribed to mailing lists with single addresses again, so now I have a single filter rule which happily can filter Launchpad mails around as well.

Happily I’ve been able to make a change I’ve wanted to for a while, home and work e-mail is separated into different Maildir/ trees; and mailing list subscriptions made with the most appropriate address.

The magic of dovecot lets me create a fake scott+canonical user that uses the alternate Maildir tree, while still retaining my user permissions, etc.

Overall I’m pleased with the new setup, and how the migration went. SpamAssassin needs some tuning as a little SPAM is still getting through, but otherwise it seems to be working well.