This error occurs sometimes, mostly in Netscape Browsers, version 4.7x
The first step to trouble shooting your problem is to make sure you are typing the correct password. (Remember, usernames and passwords are case sensitive)
If you still get the Username/Password Mismatch error, then you will need to verify that you have the correct settings.
Normally, your settings to check your e-mail should be as follows:
Example E-mail address: you@yourdomainname.com
E-Mail Username: you@yourdomainname.com
E-Mail Password: yourpassword
Incoming Mail Server: mail.yourdomainname.com
Outgoing Mail Server: mail.yourdomainname.com or use your ISP SMTP Settings
However, if you have the correct settings as detailed above, and you are using Netscape 4.7x then adjust your settings as follows:
E-Mail Username: you%yourdomainname.com
E-Mail Password: yourpassword
Incoming Mail Server: mail.yourdomainname.com
Outgoing Mail Server: mail.yourdomainname.com or use your ISP SMTP Settings
SMTP Note: If you use the above smtp, sometimes your ISP requires authentication. If this is the case then you need to select "My Server Requires Authentication" and enter your ISP login and password.