I am using the built-in email with GL and when I try to sign up new users and send email I get the error:

Warning: mail() [function.mail] SMTP server response: 554 User not local. Authentication required for relay in c:exampleexamplegeeklogsystempearmailmail.php on line 113

I have NOT touched any files such as mail.php NOR have I modified the mail settings in config.php.

Running Apache 2 on MSW2K3 Ad Server, PHP 5

Any ideas?
TY
TR

It sounds like your SMTP server requires user authentication before use. Make sure you have the correct mail settings setup. Especially take a look at the settings that are part of $_CONF['mail_settings'] in config.php:
'auth' => true,
'username' => 'smtp-username',
'password' => 'smtp-password'

-Vinny

I was under the impression I did not need any of these settings when using the built-in script "mail"

It all depends on the configuration your hosting provider is using. "Mail" uses the default email options in php.ini (see the [mail function] section), which if not setup correctly, won't allow you to send email. It's problem like this that led us to providing alternative methods of posting email.

I'd suggest you use smtp and specify your host's SMTP server and authentication details.

-Vinny