Loss of email send/receive due to continuous message

I am unable to send/receive emails due to a continuous message “Password required” followed by Server says “5.7.1. Authentication failed”

The problem is most likely with your email provider if it was working before and now is not. Contact them and see what they say.

If this is a new account you have setup, check that you have entered a password. If you go to Menu > Tools > Accounts, and check on the General tab for your account that a password is entered. Maybe enter it again.

Authentication errors can occur when you have the incorrect security policies in your account settings, but I don’t think that will be a 5.7.1 error. You can check anyway. On the IMAP/POP3 and SMTP tabs check that you are using one of the following combinations.

SMTP
Port 587 = Force usage of SSL/TLS
Port 25 = Use SSL/TLS if available
Port 465 = Use SSL/TLS on special port (legacy)

IMAP
Port 993 = Use SSL/TLS on special port (legacy)
Port 143 = Use SSL/TLS if available

POP3
Port 995 = Use SSL/TLS on special port (legacy)
Port 110 = Use SSL/TLS if available

These are the correct combinations of port and security policy. The underlined ones are the best option for security if your server supports them. SMTP port 465 was reassigned and should no longer be used for SMTP, though many mail providers still recommend and use it.