Open Gmail and sign in
Click Compose to start a new email
Type the subject line in the Subject field
To change the subject of a draft, open the draft and edit the Subject field
To change the subject of an email you received, you cannot edit the original subject
To send a message with a new subject, click Reply, then use the menu to choose Forward or create a new email
In Gmail, open the reply draft and click the three-dot menu if needed
Select Edit subject if available, or forward the email and enter a new subject
Save or send the email after updating the subject line