Cannot send emails from Samsung Galaxy S7 using TypeApp

A few months ago I started having a problem sending emails from my phone when connected to my personal wifi (Cox internet).  Phone: Samsung Galaxy S7  App: TypeApp.  After failing to send the email using wifi, I can immediately turn off wifi on the phone and using the phone's data plan send the email with no problem.  I have tried two different modem/router boxes with the same result.

The Typeapp support suggested I contact my ISP with the following question:

Our app needs IMAP and SMTP ports open (993, 465, 587 and sometimes also 143, 25).

Are those ports open with Cox?  What other causes might the problem have?

Thanks,

David