Unable to email preview of newsletter

Hi,

I created a newsletter and attempted to send myself a preview copy. It failed and displayed the following error message:

Mailer Error: SMTP Error: The following recipients failed: aronson.neilj@gmail.com<p>SMTP server error: Please turn on SMTP Authentication in your mail client, or login to the

550-IMAP/POP3 server before sending your message. gator692.hostgator.com

550-(whenthemosescameagain.com) [174.132.164.2]:56272 is not permitted to relay

550 through this server without authentication.

</p>

I'm using standard Gmail settings and I have POP3 set to Enable. How do I ensure that newsletter emails get delivered for my client?

Thank you.
Neil