At work everybody has a primary email address tied to the domain, which for us is CrownSpaHotel.com.
However, some users need a different primary domain (eg. ScarboroughHotel.com) this used to be easy to do in the old days of SBS2003, in fact we had around 7 domains in exchange as secondaries.
1. Make the changes in Exchange
With Exchange 2007, this all changed with a tightening up of security and a change in processes, anyway I searched everywhere for an answer and I found an easy step by step guide here http://sbs.seandaniel.com/2008/10/hosting-multiple-domains-on-sbs.html by Sean Daniel.
2. Make the changes on your new secondary domain
You will then need to make changes in your MX records, which for me was in a plesk panel.
In plesk you need to go to the DNS settings (in the website settings bit), here is a quick guide to the settings.
As a quick rule you should have: (in my case) mail.ScarboroughHotel.com pointing to primary IP and mail1.ScarboroughHotel.com (notice the 1?) pointing to secondary IP then create two MX records
priority 10 = mail.ScarboroughHotel.com
priority 20 = mail1.ScarboroughHotel.com
3. PTR Records
What is a PTR Record
You can think of the PTR record as an opposite of the A record. While the A record points a domain name to an IP address, the PTR record resolves the IP address to a domain/hostname.
PTR records are used for the reverse DNS (Domain Name System) lookup. Using the IP address you can get the associated domain/hostname. An A record should exist for every PTR record.
The usage of a reverse DNS setup for a mail server is a good solution. Some external mail exchange servers make reverse DNS lookups before accepting messages originating from your mail server
So basically unless you want your mail getting flagged as SPAM, you need a valid PTR record on the static IP’s you use to send mail on.
Having set all this up – it all started working! But I then had a panic attack, PTR records!
You normally setup PTR records when you first setup your SBS system – this is so everyone in the internet world knows who you are – otherwise your mail might be classed as SPAM!
I had already set these up for the primary domain, so I naturally though I would need to set them up for the secondary domain, in fact you can only have one PTR per broadband line (with static IP) or internet IP!
However, as long as the IP you are sending from has a valid PTR record and it is corresponding to a valid A record you are fine, it validates the IP, so you do not need to set up another PTR record.
Now this bit was good to read of, but I have to admit it took me ages to find this very simple fact out!