I was having a niggling issue when bouncing back and forth between the macOS Mail app and the web interface of Gmail. If I started composing an email in Mail I found that when I went to view the inbox via the Gmail web interface I was presented with a litany of (mostly) empty Draft messages. Annoying.
There was a simple solution which I found in Mail's Account Preferences. It is thus:
- Fire up Mail
- Go to Preferences...
- Select Accounts tab
- Select Gmail IMAP account
- Select Mailbox Behaviors
- Uncheck "Store draft messages on the server"
- Life and your inbox are in harmony once again
The account preferences for draft messages should look like the following: