Modify the outbound domain in Exchange

Hello Support,

I have a scenario where the company needs to keep the appearance of an internal resource but have Exchange send it out to an external resource.

Here is the scenario. The company has multiple accepted email domains on Exchange 2013. One of them we will call I need to have Exchange change any emails that are sent to to be sent instead to
So for example , Jon Doe sends an email to , I need Exchange to accept this but then deliver the email to

I checked transport rules but do not see a way of doing this.

Any help would greatly be appreciated.
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Will SzymkowskiSenior Solution ArchitectCommented:
What are you trying to do exactly? Do you have 2 mailboxes one with and another mailbox with

Or do you have a single mailbox that has 2 email addresses one for and another for

You can only have 1 primary smtp address (sending address) at a time. So basd on what you have setup will determine what needs to be done.

RMChelpAuthor Commented:
Sorry I know its a confusing one.  I am looking for more than a  "behind the scenes" relay pretty much.  I want it so that anytime a user sends an email to , Exchange accepts it but changes to The reason for this is because the External.Com server has to have the received email with their domain in it and not a relay from another server but the end users are supposed to think they are just sending an email to internal resource and not know that it actually gets sent to external resource.
Simon Butler (Sembee)ConsultantCommented:
You are trying to overcomplicate this.
If you want to send an email to an external address but using an internal address, just create a mailbox, then forward it to the external email address. Users will see the mailbox in the GAL, but not know it has gone out.

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RMChelpAuthor Commented:
The mailbox approach does not work because this is being used for faxes which means the actual destination always changes.
Simon Butler (Sembee)ConsultantCommented:
Anything else that you have failed to mention?
As that last post has completed changed what you are asking.
There was no indication that the recipient would constantly change, or that this was just a fax service.

If you had made it clear what you were trying to achieve, then it would have made answering the question much easier.

The easiest way to deal with this is to use a third party tool to rewrite the headers. You tell the users to send to and the header rewriter changes it to the actual address the email needs to be sent to.

RMChelpAuthor Commented:
Sorry if it anything was left out. It was a difficult question to word.

Anyways yes a 3rd party solution would do this but I was wanting to know if Exchange could accomplish it.
Simon Butler (Sembee)ConsultantCommented:
Header rewriting is only available in Exchange when you use an Edge server. I wouldn't deploy an Edge server for just this functionality - a third party tool will be much cheaper.


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