Unable to send mail through Google account: 535 Authentication Failed

Unable to send mail through Google account: 535 Authentication Failed

I cannot send any outgoing messages for over a week now. When I do I receive the following error:

Technical details of permanent failure:

Google tried to deliver your message, but it was rejected by the relay  smtp.zoho.com  [165.254.168.48].

The error that the other server returned was:
535 Authentication Failed

I attempted to change my password hoping this would remedy the issue but it will not authenticate my account.  Please send suggestions to correct problem.