trying to use Gmail SMTP servers for vB emails, but it's not working

[Fangs404]

I originally posted this in General, but it wasn't getting any attention, and I can't bump that thread, so I thought I'd put it in here where it probably should've been originally (oops).

I'd like to use Gmail's SMTP server to send all forum emails because we've been having some issues sending emails. A lot of free servers will accept them from our server (like Gmail and Yahoo!), but most school and business email addresses never get the email confirmation sent to them. I figure that using Gmail's SMTP server will fix this, but it's just not working. Here're the settings we're using:

SMTP server: smtp.gmail.com
port: 465
SMTP username: [username]@gmail.com
password: [password]
SMTP secure connection: TLS

When running the diagnostic, there's a delay of about 30 seconds, and then we get this error:

Pertinent SMTP Settings
SMTP: tls://smtp.gmail.com:465
SMTP Username: [username]@gmail.com

The mailing function returned an error while trying to send the mail.
The following errors were outputted by PHP when attempting to send mail:

Warning: 0 Unexpected response when connecting to SMTP server in [path]/includes/class_mail.php on line 601

Does anyone have any idea why this is happening?