SMTP Settings - Not Sending Email

SMTP Settings - Not Sending Email

After a bit of troubleshooting, I was finally able to get the incoming email settings correctly configured for ServideDesk, but I've failed to get the outgoing mail settings correctly and SDP isn't sending out replies or notifications. I'm running Windows Small Business Server 2008 with Exchange Server 2007. 

I've tried everything I can think of - including altering the mail server name, using authentication, etc, and nothing I've tired seems to work. I've checked the Firewall, but I don't see anything there (though I'm not sure what I'd be looking for). I'm having the same SMTP trouble with AssetExplorer and Desktop Central. 

Can anyone help point me in the right direction?

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