My MacBook Air trash, junk, deleted mailboxes have disappeared

..BSJ900..

Perhaps you may need to learn how to rebuild Apple Mail as it pertains

to your user account in MacBook Air? Without knowing if it also effects

any other Mail users; who may/not share your Mac, &/or access email.

• If emails appear to be missing in Mail on Mac - Apple Support

//support.apple.com/guide/mail/if-emails-appear-to-be-missing-mlhlp1224/mac

• Mail User Guide for Mac {Table -of- Contents} - Apple Support

//support.apple.com/guide/mail/toc

• Report and block spam in iCloud mail - Apple Support

You may find additional details; some could be useful, in User Guide.

At the top of the mailbox list is a section named favorites. Below that will be sections for each email account you have on mail. For instance, you might have an iCloud account, a Gmail account, or an account named for your Internet service provider. In each of those sections you will see mailboxes that are on those email servers.

If those folders are missing from the favorites section, hover your cursor over the right side of the favorites label and click the plus button. You can then choose the mailboxes you want to appear in favorites.

also, in the header of each of the sections, there is a disclosure triangle on the far right side. If you accidentally clicked that it would hide all of the folders in that section, click the disclosure triangle again to show them all.

if they are missing from the account sections in the bottom part of the list then there is something wrong with your email account. I don’t know of an email service that will allow you to delete those folders.

Dropped from the account specific section of the mailbox list.

That would imply they were deleted from the server. Can you access the email accounts from their Web portal? If so, see if they are missing there, too.

Those mailboxes should not be deletable inside of Mail.

Disappeared from where?

Favorites?

Or, from the account specific section of the mailbox list?

Click on the + sign to the right of the mailbox and then select the mailbox to put back.

Use favorite mailboxes in Mail on Mac