GoDaddy recently changed their server configuration and is now blocking outbound SMTP mail in many cases. In my case, it was blocking the mail destined for my GMail account ([email protected]) for order confirmations.

To work around this, I had to migrate my email back to GoDaddy (rather than Google apps) and use the following settings in my ECT configuration.

Email address to send confirmations to: [email protected]
Email object: CDO
SMTP server: relay-hosting.secureserver.net
User name: [email protected]
Password: password