trenaptscuba wrote:
I was having some trouble after the last update, so I had changed some settings in my email (no, I don't remember what I changed). Now my deleted emails from any of my accounts in Mac Mail do not go into the Trash Folder. They seem to just disappear. I have it set for them to go to [Gmail]/Trash, hoping they would go in both my iphone Trash folder as well as my Mac Mail Trash folder.
https://discussions.apple.com/content/attachment/f98c0599-b171-43c5-a08b-8acc73307f12
Not sure what to tell you there...
This is what I have set and it seems to work like it always did.
I do not use gmail account.

ref: Mail User Guide for Mac
For problem accounts the go to way to sort things out is to delete the account(s) from the Mail.app, then add it back.
Remove email accounts in Mail on Mac
Remove email accounts in Mail on Mac - Apple Support
Add email accounts in Mail on Mac - Apple Support
Add email accounts in Mail on Mac - Apple Support
Note—
IMAP accounts stay on the server, so no local loss, when you re-sync
POP accounts download and remove from the server—therefor save your inbox/sent box if you want them
“On My Mac" is just that, local folders you created and moved mail into. So no loss
if no insight you can call—
Customer Support (800) MY–APPLE (800–692–7753)
or on line https://getsupport.apple.com/
Outside the USA—Contact Apple for support and service by phone
See a list of Apple phone numbers around the world.
Contact Apple for support and service - Apple Support