SMTP Error in SSRS in Integrated Mode: The transport error code was 0x800ccc13

First of all I can manually send out emails from the server running SSRS using Telnet over port 25.  And the SMTP server is on the same server running SSRS.

The SharePoint based SSRS Reports are not massive by any means, and I've tested a couple subscriptions on different reports.

Nonetheless when I create a subscription for a SharePoint based SSRS Report (again running in integrated mode), the error message is:  "Failure sending mail:  The message could not be sent to the SMTP server.  The transport code was 0x8000ccc13.  The server response was not available."

Network Service is running the SharePoint - 80 website.

Any thoughts appreciated, thanks.