Dear,

I have the following environment:

The company bought the company dominioA.com dominioB.com.

Both companies have mail system.

Company A wants to standardize the environment and wants only the mail platform remains in Exchange 2010 mail servers Company A.

to have many users, and also change the MX ip address, the company does not want to do all of one.

As I raise the following:

One Accepted Domain was created with the dominioB.com

An email policy which I think I will do that by creating the accounts you create them in an organizational unit and change them to dominioB.com SMTP.

Send mail testing was made from those accounts to accounts dominioA.com and there were no problems.

Send mail testing was done from the dominioB.com account to an external account and it worked.

Send test mail dominioA.com to DominioB.com and began to bounce post is made. because the mail server is in the domainB, and server Only the domain was created. for this to work one must change the MX, but the company wants to do it gradually.

As I can do ????

Waiting for your comments

Hi,

According to your description, I notice that you have two company, Company A and Company B. Then want to deploy only one Exchange server for mail flow.
If I misunderstand your concern, please do not hesitate to let me know.

If you want to deploy Only one Exchange server SMTP name for two company, I suggest we can deploy forest trust and linked mailbox for Company Bs user.
More details about Deploy Exchange 2010 in an Exchange Resource Forest Topology, for your reference:
https://technet.microsoft.com/en-us/library/aa998031(v=exchg.141).aspx

Best Regards,
Allen Wang

Dear,

the option is good, but costs can not be taken. We will review an accepted domain or a remote domain.