On Tuesday 01 June 2010 15:42:18 Phil Howard wrote:
I see no documents in the Dovecot documents wiki on how Dovecot features can be used in the fight against spam. One hit came up in a search, and it was about how to fight spam in the MoinMoin Wiki itself (e.g. TextCHAs and such).
I guess you'll have the mental transfer of "fight spam" into "cause dovecot to perform this and that action" yourself. The possible actions are, in general, documented.
I already asked in another thread about removing message files at the search from a designated "learn-spam" folder. My next question would be how to automatically place detected spam into a specific folder for the user to access or ignore as they deem fit.
You need to configure the MTA to accept and tag spam messages, e.g. with Amavis D_PASS policy and appropriate tag levels. Then the most flexible way to put the mails into a spam folder is to use the deliver plugin for sieve, which can sort and filter mails depending on many different conditions, like presence and/or value of any header. You can deploy a single system wide default script for all users, which can be complemented or overwritten by individual users (depending on configuration).
See http://wiki.dovecot.org/LDA/Sieve If you use dovecot 1.2, using the new Dovecot Sieve plugin is highly recommended above the old CMUsieve. See http://wiki.dovecot.org/LDA/Sieve/Dovecot
The really recommended way nowadays is different though: *reject* as much spam as possible in the MTA in the receiving SMTP dialog, with a combination of blacklists, sender validation (e.g.DKIM), potentially greylisting (as you deem appropriate) and lastly content scanning with s.th. like amavis+spamassassin. I'd not expect a noticable amount of false positives, and in the rare cases the sender will be notified. The false positives rate of users scanning through a folder of tagged mail will be higher.
A wiki document on how Dovecot helps (or how to help Dovecot) in the fight against spam, I think, would be helpful.
A howto-like page to describe the usage of some dovecot features in an anti- spam context wouldn't hurt, OTOH there is not much anti-spam specific stuff at all at the dovecot side.
Rainer