we have our exchange server 2007 (10.10.2.11) at work with domain "dddddd.com" and ironport and it work just fine!

we need to test some thing at work with Exchange 2010 !!

so we came up with this idea:

we created a locked network and install firewall (10.10.2.88) the locked network has it's own DC and Exchange servers! we used the domain "dddddd.loc" any way it will be deleted!

IPs DC 10.0.0.1 EX 10.0.0.11

now the Exchange server up and running

in the firewall (10.10.2.88) we opened the ports and forwarded it to the Exchange2010 (10.0.0.11) in our main DC we defined the zone dddddd.loc to the firewall and the MX records as well

but when we test we get error

now how to make it so that the 2010 will send email directly to the 2007 (we will not use it to more that that)? and the 2007 will send the email to 2010 if the email has the domain dddddd.loc

?