Hello, If I apply address rewrite and therefore usera@test.com is changed to user222@bla.com My question is when an e-mail is replied back the mailserver will search for bla.com Does this mean that I have to also add bla.com as an accepted domain to receive mails for usera@test.com ? Thanks

Hi, If you have a second domain, to send and receive e-mail from this domain, you must add that domain to accepted domain.

and If I don't therefore message rewrite will not work correct

That's correct.

Hi, When you want to receive replies to addresses that have been rewritten, you must configure those recipient mailboxes by using a proxy address that matches the rewritten external address. For this issue, if you want to receive emails for bla.com, you need add bla.com as an accepted domain. You can get more information of Address Rewrite from this document: Understanding Address Rewriting http://technet.microsoft.com/en-us/library/aa996806.aspx Best Regards, Evan Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

And then I suppose that on the way back the e-mail converts back from the bla.com domain to the original sender ?

Hi, No, it will not coverts back from the bla.com domain to the original sender. If the original sender want to receive the e-mail, he should add bla.com as an accepted domain, and add a new e-mail address to the original sender. You can know get more information from this document: Configure Exchange 2010 to Accept E-Mail for More Than One Authoritative Domain http://technet.microsoft.com/en-us/library/aa996314.aspx Best Regards, EvanPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.