address rejected by the server smtp.gmail.com.
Can anyone help me resolve this?
The sender address xxx@gmail.com was rejected by the server smtp.gmail.com.
One minute applemail is working fine, the next minute it won't send, two minutes later it will, then it won't.
What I don't understand is - if the connection doctor shows all email addresses as working (green light) and logged in, why this comes up all the time, asking me to select another server, when the server is evidently working ok.
Any help appreciated Thanks
MacBook Pro with Retina display, macOS High Sierra (10.13.3)