Email issues"cannot send mail The username or password for smtp is incorrect"

I'm using a MacBook running OS X 10.10.5 and an iPhone 5S running iOS 9.3.2.  On both the laptop and the phone my email keeps dropping out.  I start getting the message "cannot send mail The username or password for smtp is incorrect" and no amount of password resetting, account deleting or other recommended trouble shooting techniques work.  

Any suggestions?