It is not long ago that I stepped into another “everyday IT problem”…All accounts in and out work perfect with RPC over ISA configuration except 2 of them.

Those two accounts had been initialized after a copy in the AD console from other users in the same departments, having exactly the same user permissions and Exchange advanced capabilities. However those 2 accounts had something in common between them, and different from the rest at the same time.

This seems logical of course, if you consider the fact that the RPC infrastructure uses the Exchange address lists for passing credentials from the Active Directory to your Global Catalog/RPC proxy. Thus if you hide a user from this list…no matter much you try, how correct your certificates are, along with your Outlook clients correct configuration, you will never initiate a NEW connection to your Exchange RPC over HTTPS.

I say NEW, since if the connection is established once (with the user visible to Exchange Address lists), then you may hide the user again. However don’t take this for granted, since I survived over two controversial examples. The one worked…the other did not.

Hope this saves you some timeJ.

Added the following on registry  key [HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\RPC]

12.0/11.0 for prior Outlook versions

(if no rpc key, then simply create it, right click on Outlook>new key)

“DefConnectOpts”=dword:00000000 (as colleagues mention above)

Also add the following under RPC as well

“ConnectTimeout”=dword value with hex value 000493e0
“ConnectTimeoutLow”=dword value with hex value 000493e0

“RFRTimeout”=dword value with hex value 000493e0

On http://www.petri.co.il/how-can-i-configure-rpc-over-https-on-exchange-2003-single-server-scenario.htm you will find the best way to resolve it….but as we ITs are on hurry all the time, we don’t usually see what “exists” right in front of our eyes.

Download the tool called RPCNoFrontEnd (19kb) mentioned on the page (mid). Execute after putting your external fqdn. This tool will make all the necessary registry changes needed on the server part and till now I have not found elsewhere. God bless the guy who wrote it, Harry Bates.

Restart your server in order the registry changes to have effect.

Test your Outlook client Exchange connection through RPC/HTTPs (/rpcdiag if you want). It will take a while in the first time but I worked for me.

Hope this helps…I’m going to sleep now, cause I have a tough day tomorrow.

PS. The best walkarounds I have got till now are the following: