comcast email stopped working on iphone

Since I switched to iphone I setup all 4 comcast email to MAIL app, all 4 accounts were working fine until yesterday. Now it says I have incorrect password on all 4 accounts. I checked all 4 accounts on Xfinity web site have Security settings set to accept 3rd party checked. I can check my xfinity emails using their web access. But I want to be able to use the MAIL app on my iphone and it's no longer working. I called APPLE they could not offer a solution. Need help.