This solution applies to Barracuda SSL VPNs, all firmware versions.
This problem can occur when OWA is listening on a port which is different from the port that the SSL VPN is using. If for example, a Barracuda SSL VPN was configured to listen on a non-standard port and OWA is running on 443, then you can get 404 errors occurring. The problem lies with OWA not processing the Host header correctly when the non-standard port is not being listened to by the OWA server.
This was resolved in testing by either forcing the OWA server to listen on the non-standard port or by changing the SSL VPN port to match that of the OWA server. If you need OWA to still listen on 443 then go to the Advanced options on the "Web site" property page and create an additional web site identity which listens on your non-standard port.
404 errors with OWA 2007
A different issue has been discovered where 404 errors can occur on OWA 2007 if IIS is set to accept client certificates on the OWA site.
To resolve this problem, please do the following on the Exchange Server:
- Open up Internet Information Services (IIS) Manager.
- Go to Sites > Default Web Site > OWA.
- Click on SSL Settings.
- Change the client certificates radio option from Accept to Ignore and then click Apply.
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