Very few email marketers spend time on the Subject Line of an email message, but it is the most important factor taken into account for an effective email campaign. From the technical deliverability perspective as well as the email open rate perspective, subject line plays a critical role and helps increase the ROI of email campaigns.
Impact on SPAM Scores and Deliverability
As we all know, emails are delivered (to the inbox or junk mail box) or blocked based on the Spam Score computed by the email delivery servers. Lower the score, better the deliverability rate. Email Subject line is one of the contributors to the spam score.
When determining the spam score, the spam filters (such as SpamAssassin) take a close look at the subject line of the email. Take a look at the page listing tests performed by SpamAssassin and pay attention to the tests starting with “SUBJ”. The spam scores assigned range between 1 and 3. When a subject line is designed, you should make sure that all these tests are passed, so that the score can be kept to zero. Note that these tests and scores vary based on the tools / software used by email servers and ISPs.
Impact on Email Open Rates
Assuming that you have designed a technically good subject line and able to deliver to the inbox, what is the probability of the recipient opening the email? Research indicates that the subject line plays a crucial role in this area. About 60% of the recipients decide whether to open an email or not based on the subject line.
General Guidelines
Here are some general guidelines to follow while deciding the subject line: