Error with Mac Mail sorting Rules

Danielsch wrote:

I am receiving a lot of these errors relating to my Mac Mail sorting rules (just set up) since upgrading to OS Big Sur.

3 messages could not be moved to the mailbox “Check to Delete Yahoo”

Mail was unable to open this mailbox on the server “p36-imap.mail.me.com”.

The server returned the error: Mailbox does not exist (took 8 ms)

Appreciate any advice on how to prevent/fix these errors (apart from just deleting rules, I guess, as i'd like to keep them in place).

See if there is anything here:

Rules:

Change Add Rule settings in Mail on Mac - Apple Support

https://support.apple.com/guide/mail/change-add-rule-settings-cpmlprefrulesadd/mac

Filter emails in Mail on Mac - Apple Support

https://support.apple.com/guide/mail/filter-emails-mlhl1f6cf15a/mac

Use rules to manage emails you receive in Mail on Mac ...

https://support.apple.com/guide/mail/use-rules-to-manage-emails-you-receive-mlhlp1017/mac