Why can't I delete trash in my email accounts

[AC Question]

I have 3 separate email accounts on my phone. Between the 3 I have tons of trash emails that I can't figure out how to empty it. There isn't an option anywhere for me to empty it. Can someone help me?

 

[ManiacJoe]

Which phone?
Which version of android?
Which carrier?
Which email app(s)?
Which email providers?
Which email protocol for each provider (pop3, imap, exchange)?