It is proper Netiquette to use a descriptive subject line. Do tell what it’s about in the subject.
Subject Line Netiquette For Email
A descriptive subject line for an email increases the chances of the message being read by the recipient because they know what the message is about.
Email Subject Line
When a person gets an email message in their inbox the senders address and subject of the message appear. Recipients read messages more often when they know what they are about.
Subject Line Netiquette
Use a descriptive subject line to ensure it gets read because we delete messages based on subject.