On Thu, Feb 09, 2006 at 10:17:08AM -0700, Jesse Norell wrote: > > You can have both too: SpamAssassin and blacklisting. Exim4 can pass the > > mail to SA while keeping the SMTP connection open. > > That way I can decide based on several BLs and further tests if I want > > to reject or accept the message. > > My user can even decide on their own if mail is ever rejected, and if > > yes how many SA points are required. Works very well. > > Postfix can do that, too (see SMTPD_PROXY_README for how), but there are > of course tradeoffs, eg. from SMTPD_PROXY_README: > > Pros and cons of before-queue content filtering [...] > * Con: The remote SMTP client expects an SMTP reply within a deadline. > As the system load increases, fewer and fewer CPU cycles remain > available to answer within the deadline, and eventually you either > have to stop accepting mail or you have to stop filtering mail. It > is for this reason that the before-queue content filter can be used > only on low-traffic sites. [...] > I've never tried it though ... anyone else, offhand? I'd wondered if it > would cause issues at times, but I guess it's probably no different than > other times that spamassassin chokes up delivery (eg. something network > related stops responding/working).
It can cause duplicate message deliveries if the sending host times out, but the receiving host eventually accepts the message. The sending host will think delivery failed so it'll try again later. Overall, I think it's the best spam filtering solution though. Just make sure to monitor the load on your servers. xn
