Are you running a SMTP server on a Windows Server? Then you need to use the Microsoft Exchange Server SMTPDiag Tool. It will verify your SMTP, DNS and firewall settings to ensure everything is setup properly and you are able to send email.
I think this has been out for a bit, but I just came across it. Its a FREE stand-alone Hyper-V server for Windows. Think of it as as Windows Server 2008 R2 with only the Hyper-V role installed. I’m a huge believe in virtualized server; whether they are on your own physical servers or up in the cloud somewhere. The ability to save states, create templates and change out your server(s) configuration on the fly is great. This product allows you to do all of that but with very low resource overhead. I already run Hyper-V on my servers so this will be an easy switch. Any new server I configure, this will be the base “OS”.
Hyper-V Server 2008 R2 Product Page
http://www.microsoft.com/hyper-v-server/en/us/default.aspx
Windows Virtualization Team Blog