I came across a little nasty, when trying to send email from the smtp adapter. If you look down deep into it, it does something very similar to the System.Net.Mail.SmtpClient. In that it sends a mail to an smtp server.

I kept getting the error: "An established connection was aborted by the software in your host machine"

This is useful, yet not so useful.

I looked into it a bit more, tried to ensure I had the firewall open. The discovered the problem.

The virus checking software was blocking mass mail viruses, which is not a bad thing, quite handy if you get a mass mail virus, however the service was not added to the allowed programs to enabled to send mail.

So the software on the host machine, being my machine, that was blocking the mail send was the virus checking software.

I added the service exe to the list of enabled applications to send mail, and it worked fine.

Something to watch out for in the future... always check your virus software if something is not transmitting from your machine successfully. It's not always the firewall :)