IMAP sent folder issue

I have a weird problem. I'm using IMAP on my phone yet when I send from my main Comcast account via the phone it goes into the sent folder and then disappears into oblivion.
Unless I BCC myself, I have no copy of that sent email on any device including the phone that sent it. It does not happen on my secondary email. I tried removing and adding back the account it didn't help. Any suggestions?