Chris Fenning explains why your subject line should state what you need: a decision, input, or follow-up. Readers decide whether to open based on the subject alone, so put the ask there first.
Chapters
How to write great emails. Tip number 2, say what you need in the subject line. When people are scanning through their inboxes, it's difficult to tell what emails are just for information and what emails require action or them— someone to do something. If you are looking for an action or a decision, or the person you're sending your email, if you want them to do something, you need to say that in the subject line. If you don't do this, people might think your, your email is just for information or not understand the importance and get to it later than you need. So how do you let people know when you need something? Say it. Say, this is a request for a decision. I need your input, help, or advice. This is the follow-up that you need to take. A few words in the subject line will make it really clear what that other person needs to do with the email, and they'll be better prepared to read it and probably more likely to take the action. So if you want to write great emails, make sure you put what you need in the subject line.