Subject: Two internet domains on one static IP address and one domino server
You can do this with a single IP address. Both DNS entries will point to the same IP address from the outside.
On the domino server, you will need a global domain document to identify the internet domains that can receive mail on the server. Look in the administrator help files under ‘domain document’. Here is the relevant passage:
Global domain document
A Global domain document identifies the Internet domains that are considered to be internal to a Domino domain and for which the local domain can accept mail. In this document, you specify one primary Internet domain name and multiple alternate Internet domains for which the server accepts mail. The Global domain document also defines rules for converting the sender’s Notes mail address on an outbound SMTP message to an Internet address. If your organization uses more than one Internet domain name, create a Global domain document to define the various Internet domain names to which inbound mail might be addressed. By default, the Domino Directory does not contain a Global domain document.