how do I stop sent emails from coming back into my inbox

Are you automatically including yourself in your Mail preferences?

Under the first group of settings ("Composing"), you will find a checkbox that reads "Automatically [Cc / Bcc] myself" (which is unchecked by default).

Apple Mail >> Preferences >> Composing tab and verify if " cc: myself " is enabled with a Check Mark.

Details and context will help.

+1

2019brew wrote:

That box was unchecked. Thank you

Then what caused you to mark that suggestion "solved"?

No sure if Welcome and Thank you too - is appropriate

Just for testing - send yourself an email without the cc enabled what happens.