Could not connect to SMTP host. Connection refused.

Are you sure this is running on the correct server? Really, really sure? Sure it's not running on PSNT for some reason? Really, really sure?

Sometimes we spend hours going down dead-ends, expecting to see what we expect to see, when the whole time the error is right under our noses.

In this case I just spent hours, over days, trying to track down why emails from App Engines wouldn't go through the SMTP server. I was fully expecting them to be running on the Unix box, but for one reason or another all App Engines were being sent to the NT box by default, where there was no SMTP server setup.

Errors include:

Could not connect to SMTP host: localhost, port: 25 
SMTP sendMail failed (server :0).  Cannot send email to localhost, port: 25;