This keeps popping up!!!

[bakemecake]

The mail app keeps opening up a window that says "Account Expired Renew subscription now to resume service." I can't figure out how to get rid of it! And it pops up every 15 minutes, which gets inconvenient very fast. I have attached a screenshot of the accursed thing! Any suggestions? Thank you!

 

[eneisch]

Are you sure it is mail that is initiating the pop-up? Google search indicates it may be a browser extension issue. The suggestion I saw was to disable browser extensions and see if the message stops popping up. If you use more than one browser (chrome, firefox, etc.) you should turn off their extensions too. If the message stops add the extensions back one at a time or in small groups to try to identify which one is creating the problem.