reviously, I wrote about how to prevent newsletters and mailings from being discarded by spam filters. This month I am going to look at the other side and discuss spam filter options to help you staunch the spam battering your inbox.

Spam filters assign each incoming e-mail message a spam probability number. Many filters assign this probability to distinct words, phrases and attributes of an e-mail. Phrases that involve getting rich quick or free products tend to rank high and are routinely discarded.

Filters will reduce your spam. However, they tend to make arbitrary decisions, which is why having a great spam filter is a must.

Filter flavors

With all of the spam being passed around, it shouldn't come as a surprise that there are several kinds of spam filters available. I split them into three categories - painfully effective, industry standard, and silent and quiet:

Painfully effective

Permission-based or response-based spam filters are the strictest of all. People sending e-mail to a recipient with this type of filter will receive an e-mail response asking them to confirm that they are, in fact, the message's sender. In a short online form, they are asked to identify who they are and, perhaps, answer a question.

The recipient then receives the request, approves it (if it is valid) and is thereafter able to receive e-mail from that sender. If the request is not approved, no mail from that sender will get into the recipient's inbox. This type of solution is ideal if the majority of your e-mail comes from the same pool of people.

This technology eliminates virtually all spam because the process requires senders to verify that they actually wrote you. On the downside, this solution is cumbersome. It puts a fair amount of work back in the hands of the sender.

Ironically, there is also an abandonment rate because some requests for confirmation may be blocked by the initial sender's spam filter. So, some people you might want to hear from just might not get through to you.

Industry standard

The most prevalent industrial spam filters use a Bayesian algorithm to identify spam. Basically, this means they assign probability values to various phrases in an e-mail message. This is effective for the most part, but it does result in some false positives (e.g., e-mail from your best friend might not make it to you) and false negatives (which might explain those unsolicited stock tips you're still receiving).

At Nubrek, we use a spam filter with this technology, hosted by AppRiver. Every morning I receive an e-mail report telling me just how much junk mail was blocked from my inbox.

Yesterday, it indicated 286 messages were blocked. But one of those shouldn't have been snared. In the report, I was able to select the snagged message and add it to my approved sender list. Unfortunately, three spam messages had evaded the blocker. By right-clicking on those messages, I was able to add them to my blocked-sender list.

Silent and quiet

For many years I used to have two e-mail accounts: one that I provided when signing up for services and one (personal) that I only gave to friends and colleagues. My personal e-mail account stayed fairly clean, and I really didn't have to worry about spam.

Now that I distribute my e-mail address publicly, this type of filtering really isn't an option. Web crawlers grab my joel@nubrek.com address from articles like this one, which are published electronically as well as in print. Consequently I receive a lot of spam.

This approach probably isn't appropriate for your business e-mail account. It is unlikely to scale as you add employees to your business. It could, however, work with your personal account.

Imperfect solutions

Deciding which spam-filtering technology to use can be difficult. Would you rather deal with false positives and negatives or force the folks e-mailing you to prove they are a person and not a spambot?

Many people, including technology guru Walter Mossberg at The Wall Street Journal, prefer the painfully effective option, putting the burden of proof on the sender. The majority of organizations and businesses I have dealt with, however, favor the industry-standard option.

It's important to make certain users have a way to authorize individual senders and dig into problematic e-mail transmissions. When users are waiting for important messages, they should be able to check whether the messages are in the clutches of spam filters.

Some available spam filters to look into include:

• AppRiver (www.appriver.com)
• OnlyMyEmail (www.onlymyemail.com)
• CA Anti-Spam 2007 (www.qurb.com)
• ChoiceMail Free (www.digiportal.com)
• Spamihilator (www.spamihilator.com)
• McAfee SpamKiller (www.spamkiller.com).

I have not tested all the products on the market, nor is this article meant to provide product reviews. Use some filters on a trial basis until you find a solution that comfortably fits your business and style.

Taking control

Here are some things to keep in mind when evaluating spam filters:

• Make sure the spam filter you select provides virus signature updates. According to our November 2006 domain statistics report, Nubrek e-mail addresses were sent 51 viruses that month, alone.
• Strong reporting is important. You should be able to tell what your spam filter is doing and how well it's performing. In November, Nubrek.com received 12,992 spam messages. That's a lot of productivity our employees would have lost had the filter not caught those messages.
• Host your spam solution at the domain level instead of on each user's computer. Desktop-based solutions are effective if you're a one-man show, but as soon as you have an office with three or four people (many of whom may not want to spend time fixing their e-mail) I recommend a domain-level solution.
• Keep a Gmail, Yahoo or Hotmail account available in case you can't get a message through your spam filter.

Managing the flood

Microsoft Outlook's XP and 2003 versions have simple spam filtering abilities. These aren't advanced and will fail to catch a lot of spam, but they can help if you don't have a better option. Outlook's Junk Mail feature is enabled by default in Outlook 2003. If you use Outlook, you've probably already noticed your Junk Mail folder collects mail.

Outlook also provides rules-based filtering and sorting. Since I read much of my e-mail on my BlackBerry, I have Outlook sort a lot of my nonpersonal e-mail into folders. I'm on several active mailing lists, and it's not important that I always read each message right away.

To get a jump-start on Outlook's rules, right-click on an e-mail and select Create Rule. From there, you can tell Outlook what to do with all mail from that e-mail address.

Along with the barrage of spam, other types of unsolicited communications inundate us. While you are trying to trim back the junk e-mail you receive, why not take steps to reduce your postal junk mail as well? Go to www.stopthejunkmail.com It will put a stop to your junk mail for a fee ranging from $19.95 to $89.95 per month, depending on how large your company is.

And while you are at it, you can quell marketing calls to your residence and cell phones by registering with the National Do Not Call Registry at www.donotcall.gov If telemarketers call your numbers after they have been registered for at least 31 days, you can file a complaint. Registration is effective for five years.

I wish you the happiest of holidays and hope only personal holiday greetings make their way into your inbox.

Joel Rydbeck, Chief Technology Officer of Nubrek Inc., brings his strong background in e-commerce and business process automation to the merchant services industry. Nubrek offers eISO, a Web application for ISOs that tracks leads and provides automated residual and commission reports. For more information on eISO or to view a free demo, visit www.nubrek.com/eiso.html E-mail Rydbeck at joel@nubrek.com