Exchange 2007 webmail access from outside the domain

Posted on 2009-04-08
Last Modified: 2012-05-06
Hi ... I have a new Exchange 2007 server on a domain with an existing Exchange 2003 server. Only a few test accounts have been migrated to the 2007 server and they seem to work fine (can send and receive mail, have access to the GAL and Public Folders) with the exception of access their accounts from outside the domain via webmail. I can put in the private-side address of the server "" and it works fine. When I go home and try to access our public "http:\\" owa site (hosted by Exchange 2003) I get the "Internet Explorerer cannot display the webpage" error. When I click on the "more info" button I get "The problem can be caused by a variety of issues, including: Internet connectivity has been lost. The website is temporarily unavailable. The Domain Name Server (DNS) is not reachable. The Domain Server (DNS) does nothave a listing for the website's domain. If this is an HTTPS (secure) address, click tools, click Internet Options, click Advanced, and check to be sure the SSL and TLS protocols are enable un the the security section. The link that displays on the address bar on the error page points to the Exchange 2003 OWA ( It looks like 2003 OWA isn't allowing passthrough to the accounts on the 2007 server? Since I can webmail to the 2007 server within the domain, I'm sure it is some DNS setting or perhaps a setting on the 2003 OWA/IIS.

Question by:OGDITAdmin
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LVL 58

Expert Comment

ID: 24100286

The 2003 back-end mailbox server will not proxy OWA requests for mailboxes on another server to the remote server. Only a Exchange 2003 front-end server is capable of doing this. This is simply by Exchange design. You would need to connect directly to Exchange 2007's OWA for mailboxes on the Exchange 2007 server.

It is important to note at this stage that the front-end server to which clients connect for remote connectivity must be the version of the highest Mailbox Server on the network. In other words, if you want one single connection point for users to log-on to for OWA or RPC/HTTP, you MUST use an Exchange 2007 CAS server in this instance.

With Exchange 2007, you can open the port through to the Exchange 2007 CAS and have all users access OWA through that server. Since Exchange 2007 is different to Exchange 2003 by design, the Exchange 2007 CAS can proxy requests to legacy 2003 servers.


Author Comment

ID: 24100798
Hi Matt, thanks for the quick reply. This is the a small network (150 users) so there are just the two exchange servers. How do I set the port on the 2007 box to allow OWA access to its mailboxes and the mailboxes on the 2003 box?

LVL 58

Accepted Solution

tigermatt earned 500 total points
ID: 24100900

The port change required is in the firewall, not in the Exchange Server. You'd simply need to reconfigure the firewall such that port 443 goes to the IP of the Exchange 2007 box, not the 2003 server.

As some further reading, I'd suggest you take a look at with regards to OWA co-existing between Exchange 2003 and 2007.


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