We had zoho working fine with outlook 2016 for weeks and today all of a sudden it keeps prompting for a password for the smtp server.

I have reset the users password and have 2 factor turned on. i am using an app generated password and when outlook does a test, it logs onto the incoming mail server fine but keeps prompting for a password for the smtp server. I have ticked the box to say that the smtp password is the same password

Gurpreet