I deleted the Trash" mailbox, how do I get it back?

38gnocchi wrote:

This is the mailbox that is installed with the operating system

If this the Mail.app ...

move your mouse to the right side to reveal the + and add it back in:

ref: Mail User Guide for Mac

38gnocchi wrote:

What really happens: when I click on the trashcan on the mail toolbar the item does disappear but does not end up in the sidebar thrash and s nowher eto be found. Any ideas?

Verify your Mail>Settings for each account—

make changes if necessary and compare your results, then come back to your preferred setting and test.