Most spam filters use a scoring system. Each offense has a value. The higher the sum of a message’s offenses, the more likely a spam filter will reroute the message (or not delivered at all). A lone offense usually isn’t enough to flag a message as spam; it takes a combination of violations to score high enough to meet the level of true spam. But the system isn’t perfect, and sometimes overzealous filters flag legitimate messages as spam. Applying the following do’s and don’ts will help you ensure that your legitimate messages pass the spam filter test and reach their intended Inboxes.

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1: Do curtail your excitement

Specific words and phrases are the number one hook for spammers, and that makes them the best tool for catching spam. Discussions of large sums of money and amazing breakthroughs top that list. Offering a money back guarantee or a way to save money — Why pay more? — may be part of a legitimate offer, but it will set off spam alarms. Your message might excite you, but multiple exclamations points will also excite spam filters. All uppercase characters might convey your enthusiasm, but they’ll also set off spam filters. Just using the word urgent is enough to put a spam filter on alert.

Avoid using words and phrases that trigger spam filters. You don’t have to memorize a long list, just visit a few of the Web sites that maintain lists of spam keywords. Use the phrase “spam keywords” in your favorite search engine and you’ll get plenty of hits. Look for current lists, as the keywords are updated regularly. It’s okay to share good news and special offers with associates and clients. Just bypass all the hype.

2: Do use plain text

An email that consists of all HTML or all images and links will trip a spam alarm. HTML is certainly okay, as long as it’s good code and it doesn’t comprise the entire message. Sloppy HTML code is also an easy giveaway for spam.

Go ahead and use good HTML code but also include as much plain text as possible. That’s a clue to the spam filter that the email is legitimate. Besides, you’ll want to accommodate recipients who choose to view the message in plain-text format.

3: Don’t include attachments

Avoid attachments when possible. Spam often contains destructive attachments, so filters tend to overreact to an attachment. Links are a better alternative, if feasible.

4: Do check your sender score

A sender score grades your reputation as a sender. Your average business or personal account probably isn’t going to learn much from this score. Businesses that rely on frequent email campaigns will. If that includes you, check your sender score often and be proactive about repairing damage. A bad reputation can result in email being filtered, regardless of content.

5: Don’t send spam!

If you maintain a large list, for marketing — for any purpose really — make sure the members of your list want your email. Sending spam will get your domain and your business blacklisted and it’s difficult to get off those lists. Once you’re on a blacklist, most spam filters will snag your mail, regardless of its content. Remember, your reputation is important as your message (#4).

Hint: Exchanging business cards is not an invitation to send spam unless that condition is made clear during the exchange.

6: Don’t use colored fonts

Black type seems boring, but in truth, it’s easy to read and looks professional and clean. Don’t be fooled into thinking that colored fonts will create eye-catching opportunities to promote your message. They might, but they’ll also excite spam filters.

7: Do test your recipient list

When you send an email or newsletter to a list, test the message in as many client applications on as many operating systems as possible. Simply send the message to yourself or to a test account and retrieve it on several machines using different operating systems and email clients.

8: Don’t use the word test in your test message

When testing an email or newsletter (#6), don’t use the word test in the subject line. Most server filters will snag the message, regardless of the message’s content. You’ll waste time trying to fix the content when that single word may be the culprit.

9: Do compose a succinct subject

Your subject line should be as specific as possible. Smart filters assume that spammers can write a reasonable subject line. What they’ll lack is detail. The more specific your subject is, the better. For example, the subject Tomorrow’s Project Meeting is reasonable but generic. A better subject might mention the time, the meeting room, and so on. Don’t go overboard, but include details if possible.

10: Do rely on professional experts

For most of us, a legitimate message that’s snagged by a spam filter can mean lost business or at the very least, hard feelings. These tips aren’t meant for professional online marketing operations. If you’re considering an online marketing campaign for your business, don’t wing it! You could inadvertently damage your company’s reputation. Hire a professional who specializes in online marketing to keep you on the right side.