<snip

This post mentions port 587
http://forums.asp.net/p/1235845/4145...+SmtpCli ent+

Here's google on port 587:

http://mail.google.com/support/bin/a...n&answer=13287

Outgoing Mail (SMTP) Server - requires TLS3 or SSL:
smtp.gmail.com (use authentication)
Use Authentication: Yes
Port for TLS/STARTTLS: 587
Port for SSL: 465

TLS: TLS (Transport Layer Security) is a way of changing data such as
your username and password into code as it travels across the Internet,
so that the data will be secure and private. With mail delivery, TLS
begins with an unsecured connection to the mail servers, and then
upgrades to a secure connection once information is sent.