Is there a way to enable the VRFY command on the Exchange server. I know this command is a security risk, but the server sits behind a firewall, and is not accessible from the internet. I would just use it as an inbox. The mail traffic would be forwarded from my home coded SMTP server, which would check for the existence of the exchange inbox with the VRFY command.
I only found this on the internet, but this is only for legacy versions of Exhange.