ISSUE: Mail 100% CPU... Big Sur.

Hello On_bn,

Thank you for posting in the Apple Support Communities. We see no one has responded to your post yet. To assist the community in replying, you might consider providing more information about what you’re experiencing. Including the following details in your post may be helpful:

What’s happening? If you receive an error message, what does it say?

What device is this happening with? Which software version?

Are you able to reproduce the issue? What actions do you take to reproduce it?

The more information you provide, the better chance the community will be able to offer some additional guidance.

Have a great day!