SMTP Stopped working

I have installed it and configured it using the settings on your site and been using it without problems for some time in thunderbird. Lately I can not send mail anymore as it keeps asking me for my password which is correct as I used it to login to the web interface

Type : SMTP
Mail server: smtp.zoho.com
port: 465
security: ssl
authentication: plain
username: personal@craighaywood.com
password: <mycorrectpassword>