Of all the various services that I use/host online, I consider email to be, by far, the most critical. It’s been over 11 years since I registered my first domain name so as to have a permanent email address regardless of changes in educational institution or employer. I’ve gone through a variety of email setups in that time. I started with email included in a broader (web) hosting package, using POP (as I did throughout my time in school). Later, I tried hosting my own mail server at home, paying for a backup/relay server since my connection was unreliable.
At some point, I came to my senses and moved to IMAP, simultaneously moving back to hosted email (because, really, hosting an email server on a home machine is a mess), but with a provider that only hosted email. IMAP was, at that moment, the ultimate solution to my issues of email being out of sync between multiple computers. On the other hand, with IMAP, all of my email lived on the hosting company’s servers, so having an email hosting company that knew what they were doing was important.
The other major issue in the move to IMAP was filtering. I had well over 100 filter rules in Eudora when I stopped using POP. With IMAP, I no longer had to have filtering rules on every instance of my mail client, but I had to set up the filter rules in the framework allowed by my email host. (One provider had a Bayesian filter system that could be set to learn from every message move made via IMAP, which was cool, but slow to learn and not accurate enough.) As time went on, and through changing email hosting providers, this became very cumbersome (especially compared to using procmail on a receiving account, which is how I selectively filter the email that goes to my Blackberry).
When I finally gave up on the hosting company’s email filters, I had nearly 150 filters and there were dozens more I wanted, but just couldn’t be bothered to set up. With 150 filters and no simple way to group and arrange them, managing the filters was impossible. If I wanted to rename a mailbox that was the destination for a filter, I had to hunt down the filter and change it, which meant digging through a massive webpage listing of 150 filters. But using an email hosting provider was non-negotiable for me.
After much searching for ways to run procmail on a remote IMAP account and finding nothing, I finally settled on trying imapfilter. At first, dealing with the Lua scripting language used to configure it was tedious, but it was easy to learn and thus wasn’t a problem for long. Now, a week into using imapfilter, my config.lua file is 372 lines long–it’s doing all the filtering I’d been doing through the email hosting company interface, all the filtering I wanted to do, grabbing some spam that persistently evaded the spam filter system, and automatically taking messages that I put in my Junk folder and sending them back to the spam filter system’s reporting address. I have imapfilter running on a VPS (which I use for a variety of utility things) via cron job every few minutes. When I want to add a new filter or change the behavior of an existing filter, I can just fire up (Mac)Vim, open the remote file, and apply the power of Vim for quick and easy editing.
It’s the biggest difference in my email use since the move to IMAP. If you’re using IMAP and you want more powerful/flexible filtering, you should definitely look into imapfilter.