SUMMARY:

This is a general overview of guidelines for sending and troubleshooting outgoing / SMTP email on your domain. It is important to remember that (mt) Media Temple has secured your outbound mail server to only allow valid email users to send email through your server. This prevents Spammers, etc from illegally using your email server to send unsolicited email. You must tell the email server that you are valid email user, here is how:
Enable 'SMTP Authentication' in your email software's settings. Often this is located in the "servers" or "security" section of your email settings area. Sometimes the option is called "My server requires authentication" or it might just be "SMTP Authentication". Make sure to turn it on. If it asks, the username and password is the same as your receiving username and password (your POP account).

DETAILS:

Email Program Setup:

Turning on SMTP Authentication in your email software is very simple. this KB: Email Program Setup Tutorials will help you to set this up properly.

After this is setup, you will have trouble free, high performance email sending capability using your hosting service as a mail relay.

SOME ISP'S BLOCK OUTBOUND MAIL TO OTHER HOSTS:

A growing number of ISPs including EarthLink, Mindspring, Cox, Verizon and Verio do not allow outbound SMTP connections to other host providers, and servers. (They block port 25). You'll have to use their mail servers to send outbound mail. (Example mail.earthlink.net) If this applies to you, future support regarding these matters will need to be taken up with the ISP's tech support department. Maybe they can make an exception for you. (mt)Media Temple is unable to influence their policies.

Using alternate ports:

(gs) Grid-Service customers may use the alternate port 587 to get around a blocked port 25. They only need to make this change in their email client.

(dv) Dedicated-Virtual customers can review our article on changing the SMTP mail port and then can use the alternate port they specified to send mail.

Revisions:

07-20-2009: Minor Fixes