iPad, iPhone email settings bug?

For some unknown reason, perhaps with the latest IOS update installs... my email on both devices keeps rejecting either my password, username, and sometimes the smtp server. Comcast is my provider and my email on my iMac is working just fine with the same username and passwords. It seems no matter how many times I try to add a new account using the same username/password its verified, so I then delete the "old" account... try to send an email and I get a popup telling me the username/password is wrong or another password saying mail can't verify the server. This is happening on my iPhone 6 as well as my iPad4.

I spent well over an hour with a Comcast tech on the phone, no progress. She could not explain why its working on my Mac and not working on my iOS devices. Could there be a bug in the latest iOS 11.3?