RPC over HTTP Oh why thus tho not work externally
Error
Outlook cannot log on. Verify you are connected to the network and are using the proper server and mailbox name. The connection to Microsoft Exchange is unavailable. Outlook must be online or connected.
OR
Unable to open you default mailbox
OR
The Server is unavailable
Resolution 1
Disabled IPv6 on the Exchange CAS server http://technet.microsoft.com/en-us/library/cc671176(EXCHG.80).aspx
In summary disable IPv6 on the NIC and make the following change to your host file:
#1::1 localhost
xxx.xxx.xxx.xxx exchangesevername
xxx.xxx.xxx.xxx. exchangesevername.fqdn
then IISRESET
Resolution 2
Configure External Exchange URL and Certificate http://support.microsoft.com/kb/940726
If you are using a wildcard you will also need to configure the CertPrincipalName:
Set-OutlookProvider EXCH -CertPrincipalName “msstd:*.fqnd”
Set-OutlookProvider EXPR -CertPrincipalName “msstd:*.fqdn”
Gotcha 2: TMG! Dam! TMG! Disable pre authentication and cache filtering!:
Resolution 3
If you are publishing using ISAIAGTMGUAG would suggest changing the configuration of the publishing rule as follows:
On the Listener:
Authentication tab: No Authentication
One the Rule:
Bridging tab: Make sure SSL-SSL is selected (SSL-HTTP is not supported)
Authentication Delegation tab: No delegation, but client may authenticate directly
Users tab: All users
Under System – Web filters:
Disable Compression Filter
Disable Caching Compression
Troubleshooting Tool:
Handy little testing tool by the Exchange Team:
https://www.testexchangeconnectivity.com/
Example Platform
Exchange Server:
Windows 2008 SP2 x64
Exchange 2007 SP2 x64
TMG Server:
Windows 2008 R2 x62
TMG 2010 SP1