Surely this goes beyond the scope of a system junk cleaner?????
Forgive me if i have miss understood this but you are asking for ccleaner to remove deleted emails in the trash can?
If i have understood this correctly ccleaner would have to connect to that particular web server using httpwebrequest, (every web page is different so how would ccleaner know how that particular http renders. There is hundreds and thousands of different sites) login with your credentials, store the session then DELETE the emails on that server.
But then again i have probably just miss understood you lol