Mail uses high CPU

Hello Steve Holdship,

Welcome to Apple Support Communities! We understand your mail shows 110% in the Activity Monitor.

Let's quit your Mail app and restart the Mac: Quit apps on Mac - Apple Support

Log out, sleep, wake, restart, or shut down your Mac - Apple Support

If the issue persists, try disabling each mail account one at a time if it's more than one to help isolate the email account that's causing the issue. Then once you determine the email account that's causing the issue, check, to see if there are any emails stuck in the outbox and remove them. Check for any new emails that may be stuck sending.

Also, you can boot into safe mode to see if the same thing happens. Safe mode clears some caches and can bypass some software that can cause conflicts on your Mac:

How to use safe mode on your Mac - Apple Support

Best Regards.

Hey there Steve Holdship,

Thanks for following back up with us. We're glad the issue is now resolved. Feel free to reach back out if you need the Apple Support Communities in the future.

Have a wonderful day!