Galaxy S4 email authentification

[AC Question]

I have had my S4 for 6 months. I have two email accounts on it. One is a microsoft exchange the other is an att.net through yahoo. Just two days ago I started having an issue with the yahoo account. I can no longer send emails. I get the message email failed. I tried deleting the account and adding it back. the problem persists. When I reloaded it says the out going mail can not authenticate.
I already called att.net and they had yahoo test for issue. They are telling me it is a software issue on my phone. They told me to update my software. I checked my software has been up to date for more than a month.
Anyone have an idea of how to fix this?

 

[B. Diddy]

Open the stock Email app, tap Menu, then Settings, and check the account settings for the outgoing server. You need to make sure it matches up exactly with the information supplied by your email provider, including the SSL port, username, and password.