Mail Outbox Shows 1 but folder is empty
Macbook Air 11" early 2015
OS 10.15.6
When in Mail, and a message gets stuck while trying to send, the Outbox indicates 1 or 2 messages. But when I open the folder, there is nothing to be seen. I found a Q and A here but it was dated 2010, and it doesn't work for this operating system. Any suggestions on how to remedy this?
Thanks, Carole
MacBook Air 11″, macOS 10.15