Deleting tuscl email

I have a lot of old tuscl emails (both sent and received) and I would like to clean out my email boxes. In the extremely unlikely event that my wife ever somehow learns about this account, I would rather her not see some of this stuff, e.g., emails of me setting up liaisons, etc. The problem is that it is very tedious to delete these things one at a time, and there are dozens and dozens of them. I know I should have deleted them as I went along but I didn't think about it and now they're built up.

Is there any clean simple way to just clear out your email boxes entirely in one fell swoop? If the answer is painfully obvious or this has already been explained, then I apologize in advance for my lack of computer savvy. Thanks.