how do i stop notifications that it can't sign into Yahoo mail?

[AC Question]

I keep getting messages that I can't sign into Yahoo mail.

 

[B. Diddy]

Welcome to Android Central! It's probably because of Yahoo's new "security" measure that blocks most email clients from accessing it unless you change a setting in your Yahoo account. Turn that security feature off -- it's a fairly ineffective measure anyway: https://help.yahoo.com/kb/SLN27791.html