SMTP/CDOSys Error

Another weird one today. . . System.Web.Mail was throwing this error:

System.Runtime.InteropServices.COMException (0x80040213): The transport failed to connect to the server.

Symptoms: We were setting SMTPMail.SMTPServer to localhost. If we changed that to the explicit IP of the server that worked. It also worked if we set it to the IP of the Smarthost. It did not work if left blank.

Solution: The SMTP service was only configured to run on the one IP address. When we switched that setting to "All Unassigned" it started working. Presumably we could have achieved the same result by setting the service to run on the loopback address as well in the Advanced settings.

File Under: Technology,