Sent emails disappearing from Android Email Client

If I send a Comcast email from my Android phone configured for IMAP,  it magically disappears on both the phone and the web/server. If I send it from the Comcast email web client, it works as expected and stays in the sent folder on both.   I checked all IMAP settings etc. I have 2 comcast.net emails and this occurs in both. In addition I have other emails,  Yahoo and Hotmail on the same mobile app client and there are no issues.

My workaround has been to bcc  me on any mobile email but what is going on?