IMAP Command "APPEND" ERROR

The IMAP command “APPEND” (to Sent Messages) failed with server error: Server Busy. Please try again later. (took 3533 ms).

I've seen many others are getting this error. It seems to have no pattern when it happens. It happens again and again but randomly. In addition it sometimes affects the ability to move messages to folders. Sometimes the email gets moved back into the in box. Sometimes the email string disappears and ends up in recovered email folders (this is less common). It only happens on the mac mail iCloud account and it happens on both the Mac Desktop and the MacBook Pro.

Both are using Catalina 10.15.7 Both have specifics folders listed in the mail behaviors options.