Email often turns into a deep pit of unanswered queries and unfinished tasks, and that's partly due to vague and un-actionable subject lines. As author Jason Womack points out, when your recipient doesn't know precisely what you want, you run the risk of ending up at the bottom of the pile.
Here's what he suggests instead:
Here’s a trick I've been using for a long time. I write the subject lines of my emails last, starting out with a verb that describes what needs to be done and a noun encapsulating what the email message is about directly. Over the past few years, I've realised I consistently make requests via email asking recipients to call, schedule, view, print, sign, scan, return or confirm receipt of a document.
It's only fair to let the recipient know exactly what I need them to do when they see the email show up in their inbox so they can get to it more quickly. At my company, we've standardized the verbs used in email subjects so that everyone on our team is on the same page. For example, if I need one of my staff to take an action, I type in the subject line: "Call Susan B. today to confirm start time for Tuesday's workshop: 415-555-xxxx.' This makes it very clear what I need done and provides all relevant information as succinctly as possible.
When you address emails more like you're writing a to-do list item for the recipient, they'll know exactly what they need to do as soon as they open the email and can prioritise the task quickly. When you're vague, they have to read the entire message to know what you want, and that can cause your request to get pushed back more than you'd like.
How to Transform Your Email into a Productivity Tool [Entrepeneur via Swissmiss]