NOBODY LIKES TO BE SCREAMED AT! And that is essentially how people react to all cap subject lines. It also looks spammy. So use Title Case with your subject lines.
Here are 6 additional tactics to avoid:
Heavy use of exclamation marks!!!!!!!!
One study I read says don’t use exclamation marks at all. The reason: an exclamation mark can be a trigger for spam filters, keeping your email from ever hitting the inbox.
Overzealous use of currency $ign$ $$$$$
Similar to exclamation points, dollar signs are a no-no. (Also, the word “money” lowers open rates and can trigger spam filters.)
Including a question and exclamation in the same subject line.
Subject lines like “Want better open rates? Act now!” are destined for the spam folder. The PLING_QUERY rule by Apache, an anti-spam platform, flags email as spam if it contains both a question mark and an exclamation mark in the subject line. Plus it looks like a sleazy sales pitch.
Misspellings = missed opportunities
Typos and errors in your subject line make you appear unprofessional and unorganized. Recipients are looking for reasons to skip your email, don’t let this be an easy one.
Asking a question?
This may surprise some, but recent research suggests that asking a question in the subject line may actually result in lower than average open rates. Posing a question does cause our brain to stop and consider the answer — and many marketers have had success using this tactic. Still, I prefer benefits over questions in the subject line. (Also, the old “Appropriate person?” tactic has up to 6x lower open rates than average. Stick to the benefits.)
Lying or misleading the reader
I hope this one is obvious. Never promise anything in a subject line that the email doesn’t deliver. Not only is this tactic spammy, it can irreparably damage your credibility. Recipients will quickly learn not to trust your subject lines, resulting in a lower open rate and a higher unsubscribe rate. By the way, using “Re:” when your email isn’t part of a thread or “Fwd:” when you aren’t truly forwarding an email is subject line trickery that falls into this category.