No Email delivery from iOS email client

Starting yesterday afternoon, Emails from my iPhone and iPad are not being delivered using the iOS email app.  I haven't changed account settings and I can send emails thru the xfinity web site and also from an Outlook app on my PC.  I can also send emails thru my iCloud account.  I removed and re-installed my comcast email and no help.  iOS thinks the emails are being sent as they appear in the Sent folder and are not in my Outbox.  Any ideas what would be causing this? Also no issues with receiving email.

Update: The problem appears to be related to a specific email address. I installed my wife's email account on my device and emails are delivered.  I installed my email account on her device and no delivery.  However, I can send email with my email address using Outlook on a PC.