One of the most important issues for email marketers is making sure the message makes it to the “inbox” of the intended recipient. An often overlooked key aspect of mailing delivery — in addition to IP reputation — is the actual subject line of the email. Not only does the subject line play an important role in getting delivered, it is imperative to accomplish the main objective of getting your marketing message opened and read by the user and keeping your list active. As such, here are some subject line best practices to follow to ensure your legitimate email is not filtered as spam.

• A subject line should be as short and descriptive as possible. The subject line should be informative and true. If your from name and address are not branded, the subject line should also provide assurance that the email comes from a trusted source. A general rule of thumb is to keep subject lines between 30-50 characters.
• A strong offer can be put right in the subject line. Evaluate your content to understand the likelihood of your message hitting spam filters, particularly if a high percentage of your list is at corporate domains. Corporate domains rely more on phrases or words that have been “tainted” by the spamming community. The major web-based email clients focus on your reputation more than your content.
• The from name and address can be as important as the subject line. A strong offer can be put right in the subject line, but it is important to use punctuation and grammar carefully to ensure that you are not perceived to be a spammer by the receiving ISP.
• The ‘from’ name and subject line should work in tandem. The ‘from’ line should communicate who you are as the sender. Do your best to not change this entry frequently and make it recognizable so that recipients understand that the email was sent by a reliable source.
• If you are cross promoting a sister brand, use the subject line to introduce the sister brand and do not change the ‘from’ address of the originally subscribed-to brand. Any other ‘from’ address is likely to increase complaints. For more information on cross promoting sister brands, please see our recent post on promoting sister brands.

That said, spammers use various tactics to fool people into opening their emails. Spammers often use words that announce a big incentive or urgency. We suggest testing certain keywords or alternative words to optimize your subject lines.

• Some key words and phrases such as “act now,” “trial,” “quote,” and “guarantee” can be tested against “complimentary,” “estimate,” “be our guest,” and “giveaway.”
• While “Free” performs well in subject lines (see Experian CheetahMail’s Free Shipping Report) you might try using “our treat” or “on the house” to see what works best for your brand.
• Avoid excessive punctuation — exclamation points, multiple periods (…), dollar signs ($$), etc.
• In the past putting full words in ALL CAPS was considered equivalent to shouting. Using all caps is a practice used by spammers. Test the use of all caps and monitor any drops in open rates potentially due to filtering.
• Using ‘Re:’ at the beginning of a subject line falsely leads the recipient to think the email is a reply to a previous email. This is a misleading tactic. This tactic is not CAN-SPAM compliant and creates a poor customer experience. If the recipient feels duped into opening an email, you might see an increase in abuse rates or unsubscribe requests.

Just a few little words/phrases in your subject line can make or break the success of your email marketing campaign, not just by impacting open rates but affecting deliverability too. To learn what works best, test. Following these subject line best practices can save your client from losing both excellent reputation and good subscribers.

I recently received a subtle-yet-effective lifecycle series of emails from Delta Airlines after I had shown interest in booking a flight with them several weeks ago. What struck me about this campaign was how seamless and clever it was to trigger a loyalty-based lifecycle series based on a customer’s recent website activity.

This sequence of events all began with a regularly scheduled promotional email from Delta that I would assume they sent to all members of their SkyMiles program. This email by chance happened to remind me that I was interested in visiting Salt Lake City for a weekend in February, and I knew from previous emails that Salt Lake City happens to be one of Delta’s hub locations. From this initial email I went to the Delta website, where I browsed for flights and compared airfare. I did not make a purchase during this web session.

A mere two hours later I received my first email in the lifecycle campaign, featuring the subject line “Visit delta.com For All Your Travel Needs.” This message served the simple purpose of outlining the benefits of booking my flight through delta.com rather than another third-party site. I was particularly impressed by the promptness of this message — my interest in Delta was clearly reciprocated by them in a timely manner.

Interestingly, the correspondence did not stop there. Delta reached out to me the very next day to continue explaining the benefits of their website and to outwardly ask for me to return to their site. This second message featured the subject line “Come On Back To delta.com” and reminded me that I had an unfulfilled order waiting for further action.

Even though I did not make a purchase during this period, the email exchange I had with Delta was quite valuable in a number of other ways. These include:

• The entire decision to consider shopping for tickets was set in motion from a regularly scheduled loyalty program campaign. Newsletters can generate revenue and interest just by being in front of the customer!
• My website activity triggered almost instantaneous correspondence from Delta showing that they were valuing my business. Website analytics data integration with email programs can help businesses show appreciation for their customers when the brand is fresh in their minds.
• Web analytics data isn’t just for cart abandons — it can also be used to trigger entire loyalty and retention-based messages. Taking a long view of the customer sales cycle can impart positive brand affinity to your customers that will pay off in the long run.

The moral of the story is that even though I didn’t make the purchase this time around, chances are the next time I need to buy airline tickets I will be stopping by Delta’s website first.