We are a company in a migration process from MS2003 servers to MS2008 servers. Because of instability in the old AD 2003 domain we chose to deploy the new domain parallel with the old one. The old forest has exchange 2003 srv. The new forest has exchange 2010 srv. I want the old domain to forward mail to the new one when users has moved from the old to the new one. And be able to use the same email domain name in both forests. Is there anyone that can point me in the right direction to accomplish this? Thanks in advance.

this is a tricky one, you want to make a forest trust with 2 forest carrying the same name, i dont think that this is possible without a 3th intermidiar. Even with it will be a nice challange seen you would need to rewite the adresses forward and back. It would be better to use an edge server with adress rewrites availeble and have you new domain use a temporay mail adress domain name. All mail to and from the new domain will be rewrited by the edge transport to the temporary domain and from the point you drop the old environment you can enable the old mail domain to the new enviroment. both ways will be hard to support during the co-excistance of both domains. If the domain is small enough ( 200 or less ) you could consider a migration where you migrate all the data in the same weekend. kinda like a sbs swing around migration. will safe you a lot of troubles.

Hi, Well this can be done, either manually or by using 3rd party tools (such as quest). To do this manually configure one of the domains as authoritative for the domain. This will be the last server in the chain, so for example if mail arrives via the old environment the new environment will be authoritative. The old environment will need to be configured so that it is not-authoritative for the e-mail domain. This is just one part of the configuration. The second part is creating mail-contacts/mail enabled users in the new domain so that the GAL is just like the GAL in the old environment. There is one thing you should pay attention to, these contacts/mail enabled users will need to have an additional address which is unique and does not exist on the new domain. So for example your old domain also adds the old.local e-mail address to the user then this is the one which should be added as additional e-mail address in the new domain. Create a send connector which matches this e-mail domain and send these mails to the old exchange server. On the old exchange server create a smtp connector which sends mail for non existing users to the new mailserver. Keep in mind this is a very short description for a complex migration when doing it without tools. If you need more info please let me know. Regards, JohanExchange-blog: www.johanveldhuis.nl

Johan has a good suggestion. You just need to build a lab and start testing your migration process.