If M$ Exchange 2007 is getting you again within Exchange, you might have the same issue I had.

If I send a mail to "User Name", the mail gets delivered.

If I send a mail to "user@domain.lala" the mail returns with the error, duh "User not found".

What did I do?
Went to the AD User MGMT, checked out the legacyExchangeDN Entry.. I copied this and added it as "X500" type to my bogus user within the Exchange console.

Problem solved...

This error was solved for me by this little script:

%programfiles%\Update Services\Setup\installselfupdateonport80.vbs

With a sweet little comand:
rsop.msc

This is also very nice:
net user /domain USERNAME
(same as #id user in LINUX)

If you have 2 Domain Controllers and you want them to behave according to your subnet, go here:

Administrative Tools -> Active Directory Sites and Services.

Now set up your Sites (e.g. Berlin, London) and add the sites Subnetz to it (e.g. 1.1.1.0/24 and 2.2.2.0/24)

That should tweak your DC network...

Very EZ, so please go here:

GPEdit:
"Computer Configuration > Administrative Templates > System > Windows Time Service”

You can configure a NTP client and server...