After solving a problem with a sweet little application I discovered (more on that below), I wanted to get some feedback about a potential enhancement for IMAP: standardized, MUA independant, server-side sorting.
Currently, there are two basic solutions for sorting: handle it during delivery or handle it in the MUA. However, if you handle it in the MUA, you lose some of the client independancy and portability that imap was designed to address, as there is no mechanism to sync sorting rules between clients, and many lightweight clients don't support sorting at all. On the flip side, in distributed mail envrionments sorting at delivery time isn't feasible, as you typically have the entire mailspool owned by a single UID and mounted via NFS. My basic point is that the two paradigms for sorting have fundemental flaws that severaly limit them.
It occured to me that it would be ideal to enable sorting in the imap daemon, enabling users to implement sorting rules which are stored in their directory (similar to the other imap metadata), and which get invoked whenever mail is checked. Perhaps that is beyond the reasonable scope of the imap protocol, but in my mind sorting is a critical task that is poorly addressed and needs to be standardized. I'd love to hear opinions on this.
See, in our mail cluster environment, it's basically impossible to use procmail without forwarding your mail to our shell server (nor are we able to use the dovecot LDA). So, the question presented to me by one of my business partners was, since Outlook was shortsighted and didn't include the ability to sync sorting rules between clients, nor did they implement sorting functionality whatsoever on the windows mobile version, what options does he have to ensure proper sorting of his mail without having to leave outlook running 24x7? He doesn't want to have to wade through mailing list email on his mobile outlook, nor does he want to have to ensure his filter rules are consistent in both his outlook and our webmail.
So, I poked around in the ports tree, and found a gem: imapfilter.
It's configured via lua, supports a very rich array of actions and queries, and has proven to be very robust and lightweight. I helped him get started with some sample rules, added it to run every minute as a cron job, and boom: robust, fully featured, MUA independant filtering in an environment that can't support procmail or the dovecot LDA.
As nice as it is, it's still a personal solution. In my mind we need to have standardized, server-side, MUA-independant sorting rules that get invoked when a mailbox is checked. Thoughts?
Andy