Exchange 2003, how do we route a SPECIFIC email to an external SMTP server?

Posted on 2007-07-20
Last Modified: 2010-03-06
- We have a dynamic IP and use an in-house Exchange server.
- This has been setup recently.
- I have it setup to connect to the ISP server and download emails for the users in the office periodically.
- Not all of the emails that are hosted by the ISP are users that exist in the office and hence I have not setup those users with AD/Exchange accounts locally.
- Our MX still points to the ISP mail server.
- We have about 10 email accounts hosted at the ISP. 8 of them are downloaded to the local Exchange server and 2 users that are very remote connect to the ISP server to get their email via POP3.

With this setup, the users that do not exist on the Exchange server cannot recieve email from the office users. When an office user sends an email to one of these account, the Exchage server spits back and NDR. This makes sense to me as the local Exchange server is setup to recieve email for our domain, but those users do not exists on our local Exchange server.

What I am hoping to do is configure the Exchange server to route these specific emails to the external ISP server so the remote users can recieve email form the office users without any errors.

Can this be done?

Please help.
Question by:erisler
    LVL 104

    Expert Comment

    Your best option is to use Exchange as it was designed and have those remote users collect email from Exchange. It will save you a lot less hassle in the long term.


    Author Comment

    I see. Are you telling me there is no way to do this?
    LVL 104

    Accepted Solution

    Nothing reliable. Exchange expects to be responsible for all email for a domain and when you send email to a domain it knows about but the user doesn't exist it will NDR it. You can configure Exchange to send email for unknown users to an external server, but that limits your options elsewhere in Exchange. It also means you cannot put the external users in the GAL, invite to meetings etc.

    For the most reliable Exchange deployment you should use Exchange for all email and have email delivered by SMTP. The POP3 connector is designed to aid the transition to SMTP delivery.


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