Outgoing email fails

I've had an ongoing problem with outgoing email.  

It works fine if I send a test email from the Administration site.  

But, when sending order confirmation or using Contact Us page the email doesn't go out.  My current fix is to modify related stored procedures, but it should work as if works for most everyone else.

Has anyone else had this problem?  Any ideas of where the problem might be?

how do you set up mail from contact us page

I don't believe there is any setup to do.  I have only found one setting that relates to the Contact page.  It is Email.UseSystemEmailForContactUsForm.  I have it set to true.  It is not clear what would be used if it were false.  One can only assume that if it is set to true then the contact us form would use the global settings for email

Same problem here. I have on v1.70 and my test email works fine. But any email sent through the site via order or contact us is stuck in the Message Queue.

The same problem. Version 1.6.

Well, I upgraded to version 1.8 and the problem seems to have disappeared.  I'll post again if for some reason the app fails in the future.

I did figure out my problem.

In IIS 6, for the Default SMTP Virtual Server > Properties > Access > Relay > Added the local machine IP (127.0.0.1). It now works.