The HDMail machine, like any other SMTP server, must have a static IP address and a Fully Qualified Domain Name (FQDN) assigned to it.
This is because any other machine that wants to send mail to the HDMail machine must be able to look up its name in DNS if it wants to connect to it and attempt delivery.
In the current anti-spam climate, many receiving mailers will perform a Reverse DNS lookup on the IP address of the sending mailer (your HDMail) to validate it before they decide whether or not to accept mail from your mailer. If your mailer does not have a FQDN registered in DNS and also a proper pointer "PTR" record in DNS, this reverse lookup will fail and many mailers will refuse to accept mail from you. Good mailing practice suggests that you correctly register the FQDN of your server.
System Requirements
CPU:
Two 2.4GHz Pentium 4 processors or equivalent
RAM:
2GB or higher
Disk:
30GB available disk space or higher
More detailed information can be found in the HDMail installation guide.
