send/receive mail from internal/nonroutable(local only) domain and external/routable domain

we have exchange 2003 in our company, and have all our users set up on our internal network, RFC1918 IP address, non-routable domain - "ourcompany.internal" for example.

we also have an externally hosted domain "" for example, where we send and receive mail to the outside world.

We can send email/meetings/etc both to and from users on our internal domain "user1@ourcompany.internal" and can even email/meetingrequests to the outside world, though any respondses fail since "ourcompany.internal" is not a valid FQDN.

We can also, from within the network, access the remote "" server and send/receive email via SMTP/POP3.

Is there a way to configure the exchange server to deliver exchange "@ourcompany.internal" email internally (as it currently does) but if the destination user is not internal, to use the "" email address for delivery so people can respond.

We do have everyone's outlook set to default to their "" account, but when they are selecting/scheduling users via calendar/appointments, it selects and sends from/to their exchange "@ourcompany.internal" email address, when we would prefer everything to be routed through the "" accounts so it reaches people remotely and can be responded to - especially if it includes people not on our domain.

This is similar to the question 21061241 to some extent;
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Do you have your email on another server other than Exchange?
If that is the case then you need to correct that. Exchange needs to handle all email, internal and external. You can change the recipient policy so that your external address is the default, but that will affect internal email delivery as well. For example if you send to another user on the same domain then email will be routed on and stay on Exchange. However if all users are on Exchange then it shouldn't cause a problem.

daveathsAuthor Commented:
yes we have email on another server other than exchange. email is hosted outside our network, and we have to send/retrieve from that server any mail destined for the internet (could relay through our internal exchange server as well I guess)

user@ourcompany.internal is our exchange server and is hosted internally on our network.  Mail (et al) for this is handled internally only, though we can send with these accounts to external email addresses...  just the replies don't work since the source email address is non-routable.
You are not using Exchange as it was designed, and as such you are going to find it close to impossible to do what what you want to do. I would actually go as far as to say you have two choices

- use Exchange as it was designed, so stop using the external hosted service and get Exchange to handle all email.
- remove Exchange.

Anything else is not going to be workable and must be a headache for the users as well as internal support. I am surprised that you can send email from Exchange with no routable addresses - you must be lucky with the recipients. Most antispam filters would block those.


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daveathsAuthor Commented:
Not discounting your response, but the primary need for exchange in this situation is to effectively share/facilitate calendaring and appointment setting, as well as provide ready access to public message stores, and provide centralized backup of mail folders/information.  Internal email is not actually a requirement of the organization, with the exception of its necessity in provisioning the above services.

Realizing that the solution may be castrating the functionality of exchange as a mail server, is there a way to accomodate the use of an external non-exchange mail server for mail, while enabling exchange to accomodate the other requirements listed?
Exchange is an email server - that is its primary task. You cannot pick and choose Exchange features to implement - certainly not removing its email functionality. Based on your requirements I would not have suggested Exchange at all but another product.

The simple fact is that you will not get Exchange to work in the way that you want. It will always want to be the main source of email and email will go out through Exchange. It either needs to be deployed correctly and fully or removed.

Most of the time I see this request from SBS users as they are able to pick up Exchange at a heavy discount from the full product.

daveathsAuthor Commented:
Bang on with the assessment, they have a SBS server installed.

Appreciate the analysis and response.
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