Unfortunately, there's no good way around spam filters: They're a necessary evil because spam continues to grow in volume. Late last year, for example, the spam-tracking company Brightmail reported that the volume of spam climbed over the 50% mark for the first time ever: There's now more spam in general circulation than valid E-mail!
The new U.S. "Can Spam" legislation isn't likely to help much, although it may force some of the more obnoxious U.S.-based spammers offshore. But once in a spam-haven, they'll continue much as before.
And spammers are getting smarter, too. You've probably gotten some spam mails with long blocks of nonsense verbiage at the bottom, for example. These spams are intended to overwhelm Bayesian filters by altering the context in which the spam trigger words appear.
But, despite the problems that all spam filters have, Bayesian filters are still the best available choice; blocklist/blacklist-oriented filters are still the worst. We all have to use spam filters, but make sure you're using a good one; keep it up to date with the latest detection rules; and verify its operation by checking what's being discarded from time to time. Odds are, you will find valid messages tagged as spam and thrown away, no matter what filter you use.
There are other steps you can take, too. For example, when you send E-mail, don't assume that your outbound messages will be received and read by your recipient until and unless you've established prior contact and have whitelisted each other's E-mail addresses. For initial contacts (the type of E-mail we tested), it might be best to open communications with a very short message--just a line or two, with no words or phrases likely to trigger a spam filter--to let the recipient know who you are, and that there's more mail on the way from you. That way, they can get your address whitelisted before your real message arrives.
Business mailers might try something similar. Instead of sending out a long E-mail, you might try sending a very brief E-mail with a link to a Web page that contains the real message. Or, in your initial contact, keep your message very brief and as un-spamlike as possible; and include information such as the domain or IP from which all your business E-mail will be sent to assist your recipients in presetting their filters to let your mail in.
The one thing you cannot do either as a business mailer or as a private individual is simply to treat E-mail today the same way you did even as recently as a year ago. The E-mail world has changed: It's now almost certain that some of your legitimate E-mails are getting trashed on their way to or from you.
E-mail has become horribly unreliable, and we all need to adjust our expectations--and actions--accordingly.
What's your take? Have you had valid E-mails filtered incorrectly? What filter do you use, and what's your experience been? Do you have a way to track what's been filtered or discarded, and if so, what percentage of false-positives are you seeing? Join in the discussion!