change AD domain name

Below is my environment

2008 R2 DC1 : - Primary DC
2008R2 DC2 : - Secondary dc
2007 Exchange server :

Now i need to change my domain from to

what will be the suggestion?
Should i need to cross forest migration from to or I can change the domain name ?
 Once I will change the domain need I need to migrate all mailboxes from to in office 365.
and I need to remove from my whole environment.

What will be the best practices? Kindly suggest...
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If you wanted to change AD domain name, its not possible because You cannot rename AD forests \ domain which has Exchange 2007 and above
Either you can create new AD forest with new Exchange 2010 \ 2013 with required SMTP name space and do cross forest migration.


If You just wanted to add new SMTP name space instead of domain rename, you can simply add one more accepted domain named in existing Exchange and then you can move your Exchange to O365
rigelnetAuthor Commented:
IF I will add the as accepted domain and add smtp of then I can migrate my mailboxes from exchange 2007 to office 365 portal in which i have register domain. After that my emails will work fine from the office 365.

Then I need to configure directory sync between my AD and office 365 to sync the domain passwords. How is it possible? because still my all the users are in and all client system are member of

Kindly suggest...
O365 have its own directory (Azure AD) which can talk to your on premise active directory with the help of ADFS and DirSync servers
There is no need to have both O365 and on premise AD have same name.
U can have as AD domain on premise and as Azure AD and both can sync users from on premise AD to azure AD with the help of DirSync and also you can use ADFS servers to have SSO for O365  outlook access
No need to change AD domain name for that.

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rigelnetAuthor Commented:
Thank you
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