That's not a decision hMailserver can easily make, as hMailserver relies on the TCP/IP stack in your system for the transport. Therefor the outgoing interface is decided by the routing decision your kernel makes. Typically you will have a routing table like this:
IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.0.42 192.168.0.16 266
127.0.0.0 255.0.0.0 On-link 127.0.0.1 306
127.0.0.1 255.255.255.255 On-link 127.0.0.1 306
127.255.255.255 255.255.255.255 On-link 127.0.0.1 306
192.168.0.0 255.255.255.0 On-link 192.168.0.16 266
192.168.0.16 255.255.255.255 On-link 192.168.0.16 266
192.168.0.255 255.255.255.255 On-link 192.168.0.16 266
224.0.0.0 240.0.0.0 On-link 127.0.0.1 306
224.0.0.0 240.0.0.0 On-link 192.168.0.16 266
255.255.255.255 255.255.255.255 On-link 127.0.0.1 306
255.255.255.255 255.255.255.255 On-link 192.168.0.16 266
===========================================================================
All traffic to the internet (0.0.0.0/0) at this system goes from Interface 192.168.0.16. Even if you add a second interface with the same gateway, netmask and metric the computer will just pick one of the two and always use that one. So there is no easy way to do what you want.
You'll definitely want to use the ADMT for this process. The version you use will be dependent on what systems you need to migrate. For example, if you need to migrate Windows 7/ or server 2008 R2 machines, you will need to run ADMT v3.2 which can only be run on a Server 2008 R2 install. If you have no Server 2008 / 2008 R2 / Windows vista / Windows 7 machines, you can use ADMT v3.0 which can be installed on Server 2003.
As Mark pointed out you can't use ADMT to migrate a DC. You'll want to start out your migrations by DCpromo'ing out one DC at the site you are migrating. When that is completed and fully replicate throughout your topology (replmon.exe is good for checking this), you can then use ADMT to migrate the server. Once it has completed migrating, you can then DCpromo it into the Root Domain.
DNS should be installed on the DCs, if not already, and AD will replicate your AD-I zones (root domain zone) to the DCs added to your root domain. You will need to re-authorize you DHCP servers once they are migrated over to the root domain (needs an account with Enterprise admin privileges).
I have found the following migration order to work well for me:
- Migrate Groups
- Migrate Users (rename the conflicts before migrating, it will save you a hassle)
- ADMT will set your users to change password at next log on after migrating
- If you don't want them to have to change the passwords, set each user to not have to change.
- DCpromo out one DC, Migrate, DCPromo into new Domain
- Migrate any other File, and Application servers (be sure to plan for the impact on applications and verify with Vendors on changes that need to be made).
- Migrate PCs
- DCpromo out 2nd DC, migrate, DCpromo into new Domain
With proper planning the impact on users should be extremely minimal. I have done migrations of full sites of 100+ PCs, and servers in a maintenance window of around 6-8 hours.
There are other things that you will need to consider like using the Password Export Service to migrate passwords.
Best Answer
Yes and no.
The first domain in the forest is knows as the "forest root domain" and shares a name with the forest. So, in the configuration that you're describing, you'll actually need three domains. The forest root will be
abc.com, then you can have two new tree-root domains namedxyz.comanddef.com.