John-
This is an error from the SMTP server you are trying to use. Most of the time this particular error comes up if the provider you are trying to use does not support SMTP or has blocked access to it ( Free email accounts like yahoo sometimes have this blocked until you upgrade to their premium email service).
-Michael
Michael Melo
Product Manager
Method Integration Inc.
Website: http://www.method.me
LinkedIn: http://www.linkedin.com/in/MichaelMelo