Tip: examine exactly which rules were triggered. Take careful note of the points listed beside each rule name – low-scoring rules do not make much of a difference, it's the ones with high scores that need to be avoided.
Tip: if there's hits in the body of your mail-out, try rephrasing those sentences. We find that spam often uses exactly the same phrases, over and over again, so we detect specific lines of text, and in most cases, synonyms are ignored.
Tip: don't use similar techniques that spammers use to disguise key words, like spacing out the letters or placing punctuation in odd places in the words. The statistics for use of these techniques show that it occurs far more frequently in spam mails.
Tip: if a subscriber reports that SpamAssassin is blocking mails they want, and they did not ask their ISP to set it up – get them to ask the ISP to take them off the filtering list! We're as annoyed as you are about this. Spam filters should not be installed on an account unless the person wants it there, in our opinion, so we ask ISPs to let the users opt in to using the filter.
Tip: don't use 'bulk-mailing' tools used by spammers (ie. advertised in spam mails). These are overwhelmingly used to send spam, so we block those signatures as soon as we can.
Tip: check out Habeas ( http://www.habeas.com/ ). They use a trademarked, patented piece of text, with restrictive licensing terms that forbid its use in spam. They've also committed to suing spammers who attempt to subvert this model. Given that, as a result, we can count on mails with this token being non-spam, we're happy to give it "bonus points" and allow it through filters.
Some useful links:
Frugal Marketing: That's not Spam, That's My Newsletter! h SpamCon Foundation: Best practices for marketers: http://www.spamcon.org/directories/best-practices.shtml
Bulk e-mail HOWTO: http://spam.abuse.net/marketerhelp/bulk-howto.shtml