Creating Email Message Content Which Avoids Spam Filters

Deliverability is the Holy Grail of email marketing. Keeping email messages from being filtered into junk mail folders, or, worse, into the abyss of an ISP's bit bucket, is essential to getting messages delivered, read, and responded to. Email message content is an important factor used by spam filters to determine its fate, and it is the easiest for a marketer to control. Here are some basic tips for creating email message content which avoids spam filters.

Email Message Subject Line

The message's subject line is of primary importance. Since it is part of the email message header, it can be read, parsed, and evaluated much more quickly and efficiently than the message body by spam filters. Words in the subject can also be given more importance by spam filters when evaluating an email message.

When deciding upon your message subject, it is important to avoid terms which occur frequently in spam email messages and spam message subjects. Words which describe pharmaceutical products, mortgages, refinancing and debt reduction, investment, male "enhancement", adult-related topics and pornography all can trigger spam filters and should be avoided. In 2003, AOL published the following list of spam email subject lines which identifies some common spam terms:

AOL's 'Top 10 Spam Email Subject Lines' of 2003:*

1. Viagra online (also: xanax, valium, xenical, phentermine, soma, celebrex, valtrex, zyban, fioricet, adipex, etc.)
2. Online pharmacy (also: 'online prescriptions'; 'meds online')
   
3. Get out of debt (also: 'special offer')
4. Get bigger (also: 'satisfy your partner'; 'improve your sex life')
5. Online degree (also: 'online diploma')
6. Lowest mortgage rates (also: 'lower your mortgage rates'; 'refinance'; 'refi')
7. Lowest insurance rates (also: 'lower your insurance now')
8. Work from home (also: 'be your own boss')
9. Hot XXX action (also: 'teens'; 'porn')
10. As seen on oprah

One example of this we saw at Savicom was a customer who was sending a 10% discount coupon to select customers to drive traffic to their site. In testing they saw it ending up in Microsoft Outlook's "junk email" folder. Our support team was able to diagnose the problem as Outlook's spam filter determining the message was spam based on the phrase "10% discount" being in the subject line when Outlook's junk e-mail protection setting was "High". Removing the term "10% discount" caused the email message to be delivered into the inbox.

Email Message Body

There are several things which can appear in the body of an email message which can cause it to appear to filters as spam. The most common things include:

• Words and phrases commonly associated with spam
• Overuse of capitalization, symbols like dollar signs and exclamation points, and misspellings
• HTML email messages containing a large single image and little or no text
• HTML email messages which contain HTML syntax errors, or which contains HTML coding styles sometimes associated with spam
• Links to certain web sites associated with spam, or links to "https:" URLs, which are often filtered to prevent phishing

Testing Your Message

It is probably not practical to test your message against every email client, spam filter, and ISP filter, however there are some basic steps you can take to check how "filter-resistant" your email message is:

• Some email service providers provide integrated spam filter checking with their services. This can be the most valuable check you can run since it can identify specific things within your message which can be problematic, making them much easier to correct. [Editor's note: All of Savicom's email marketing solutions come with a spam filter checker which runs messages through an actual spam filter, and provides a detailed report of all of the things within the message that the spam filter found that might cause it to be filtered and their relative importance]
• Run spelling and grammar checks on your copy.
• Perform basic HTML validation on your HTML email messages and correct any HTML syntax errors.
• If you have a copy of the most recent version of Microsoft Outlook, set up a test mailbox and send the message to the mailbox with various "junk email" protection settings to see if they get filtered.
• Set up accounts with various free webmail providers (e.g. Hotmail, Yahoo, Gmail) and send the email message to those accounts and see if they end up in the inbox, bulk/junk email folder, or not delivered at all.

With these guidelines, you will be able to make your email messages much more filter-resistant, and achieve better deliverability and response rates.

More resource for learning about and understanding spam filters:

• Microsoft Outlook 2003 Spam Filter: Under the hood
  
• SpamAssassin spam filter list of spam tests performed