Mac Mail Mailboxes Disappeared

Greetings.

OK, here's something else:

If I highlight an email and then go up to Message and then Move To, a list of my personal mailboxes shows up (but not the missing business ones). When I scroll to the bottom of that list there is a line that says On My Mac. That then opens a short list that includes Import which then opens to a partial list of my business mailboxes!

Yes, I did originally import some of those mailboxes over from an older iMac to this one, but the list includes newly created mailboxes as well.

???

Greetings.

No, no change.

I know the mailboxes exist, as I am able to find one by typing the mailbox name into the Mail search box and then the contents of that mailbox will show on the list of messages. However, since there are over 100 mailboxes for this account, it's not really practical for me to operate in that fashion. Plus not being able to move new emails into the appropriate mailbox.

So they are there, only they are not.... How to get them to show up?

Greetings.

Yes, it is enabled. I can send and receive emails from this account. It is listed at the top under InBox, along with the other account, as well as under Sent, Junk and Trash. But no mailboxes shown - they literally disappeared overnight.

Thx

Greetings.

OK, resolved, whew.

In the Index column of Mail (the column to the far left, don't know what else to call it) there is a On My Mac heading (underneath Inbox, Sent, Junk and Trash) and if you highlight it, up pops Hide or in this case Show. Clicking Show resulted in revealing all the missing mailboxes.

So simple, and yet so easy to miss.

Nothing anywhere, and I searched and searched, says anything about this possibility. Hope this helps somebody, sure had me worried for 24 hours....

Thx for your help.