I recently added cyrus support to subversion. I didn't touch the installer yet, cyrus has to be choosed in the isp_server tab, as I'm not really sure how the installer works.
Setting up Cyrus itself is quite easy, but it's very hard to make procmail deliver correctly, as the procmailrc files are run with users' privileges, and these are not sufficient to deliver mails to cyrus (if they were, every local user could pipe unscanned mails to every mailbox).
That means there is the choice between 2 possibilities:
1) Don't use procmail. That would definitly speed up delivery for huge amounts of mails. Filtering could be done with a postfix content_filter or by a sieve script. I'd like doing it with sieve, but that would also mean that both, prochmail AND sieve scripts, would have to be maintained in future. Should not be too hard, but I wanted to mention that
Also the MailScanner would have to be replaced by something else, as a procmail script won't work with sieve. But I already found a nice peace of software that might be a perfect substitution (and even cares of partial mails, which currently get through unscanned AFAIK) - I just forgot the name, but I know where I have to look for it *g*
2) Run procmail scripts with delivery rights. Sounds simple, but it isn't that easy. Ok, running itself IS simple... but this way the users' .procmailrc files will also need to be run with these rights.
This means that users could change their .procmailrc file and do something very odd if they wanted to.
The rc files having root as owner and no write privileges for group and others doesn't help, as e.g. renaming the file and creating an own one is still possible.
Only (known) solution: Store the users' .procmailrc files (and all other files called by it) in another, not accessible folder. As all the procmail files shouldn't be changed by users in any case, this seems to be a good solution. I'd make this the standard behavoiur if cyrus is selected.