Email disappears

Very interesting. My email accounts don't show these options. Icloud email account shows trash as a folder All Trash. However, I can't find a file with this name anywhere on my machine. On my quest.com account the Mailbox Behaviors tab doesn't show any of this. I thinnk this issue started when I upgraded to Big Sur.

It appears that the issue is that the Trash folders aren't displayed in the folder list on the left side of the mail app main menu. And going through the Mail>Preferences>Accounts>Your Account>Mailbox Behaviors they don't seem to exist. Is there any way to fix this??

I got it figured out. At the top of the folder list on the left side of the mail app. main page is a small fonted line, in light gray named "Favorites". Beside it is a light gray "+". When I clicked the + it showed me folders I could add to my "Favorites" (didn't know I had any favorites). In the list was "All Trash", that's where all of the mail deleted from the Inbox went. When I added that to my Favorites, All Trash showed up with all of the deleted email in it, at least from my Qwest account. Not sure about my iCloud account. Sorry to bother you; don't know how the All Trash got hidden.

I had already checked this. I just double checked these settings and deleted a message from my Inbox. It totally disappeared and the email trash on my MacBook is empty.

How do I find out where the Trash Mailbox is set to? I do find 3 Trash folders at Mail>Local Folders>Trash.sbd but they don't appear to have anything in them.