Outlook 2007 on Vista using RPC over HTTP "OutlookAnywhere"

January 14th, 2007
by Christopher Kusek (PKGuild)

Disclaimer: The following solution does work and has worked for me. And until further notice (I find an alternate solution to this, will be my solution for now)

I ran into a bit of an awkward situation. RPC over HTTP was not working on my Vista Ultimate box when I started using Outlook 2007. I discussed with other people and they were all fine, however they were using Outlook 2003, so not clearly the indicator I was hoping for.

Having some others test with their Outlook 2007 clients, I ran into further failure to communicate, resolving in the need to find a solution!

I did find just one solution (which does work, until further notice).

This solution resides in the following registry key


With the creation of the key DefConnectOpts (set to DWORD = 0).

The DefConnectOpts registry value helps to turn down some connection optimizations added in Outlook 2007.

So not exactly what I’d prefer, but it is something which will work when you do want your RPC over HTTP Functionality to work for you.

Some awkward things regarding this is, I did not even have the RPC key present in the registry, which prompted for the creation of that key so I could set that DWORD value. So for now, anyone having similar problems with Vista/OL2007 or somesuch and are looking for some resolution, I did find success here. I’ll continue to find a “better” solution which doesn’t involve client-hacking to go about fixing it.

1. Click Start, click Run, type regedit in the Open box, and then click OK.
2. Locate and then click the following subkey:
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type DefConnectOpts, and then press ENTER.
5. Right-click DefConnectOpts, and then click Modify.
6. In the Value data box, type 0, and then click OK.
7. Exit Registry Editor.
8. Check the effect by using the NetBios name.

Error messages when you try to connect Outlook 2007 to Exchange Server: “The action cannot be completed. The connection to the Microsoft Exchange Server is unavailable” or “Your Microsoft Exchange Server is unavailable”

Some additional notes which may help resolve this problem:

Adding another dword value of EnableRPCtunnel with a value 1.

Christopher Kusek

Tags: , , , , , ,
Posted in Exchange, Informational, Microsoft | Comments (16)

  • Jonas Inghammar says:

    Thank you very much :-)

    I’ve been trying to get this to work for a few months now but with no luck before this. The connection takes a few minutes but after that it works perfectly.

    Best Regards


  • Joshua Choate says:

    I have this exact problem and was excited to try this fix, however, I did not have an RPC folder in the Outlook folder! So I added it and then made the key but no luck… Would appreciate any ideas.


  • Kevin Watson says:

    DUDE You rock!! I too had to create the RPC folder and then once I created the DWORD entry above Outlook INSTANTLY connected and my mail was sync’ing up.

    I owe you a beer or 3!!

  • Johneil says:

    Did not work for me either.

  • Ben Benoit says:

    Hey this worked great for me, Office 2007 and Vista now I can start moveing over to this new OS.

  • For anyone who hasn’t had it successfully work.
    Try out the additional registry key mentioned.

    Also, ensure that you configure the client in the correct order.

  • Cem K says:

    Well I’ll be a monkey’s uncle – unbelievable that MS are unable to patch this themselves.

    Great tip and saved my company a crap load of effort and heartache. Thanks a bunch.

  • Fadi says:

    Worked great, thanks.

  • Oleg Starshinov says:

    Thanks! Worked for me!

  • JoshG says:

    THANKS very much. I tried this a month ago and got nothing. I too did not have the RPC key and added it and then followed the rest of the instructions. I did this on two different Vista Loads with Office 2007 and Exchange 2003. Both did not work. I just reloaded Vista, did all the updates, Office too, and still nothing. I have been able to connect via a VPN until just now. I went back in to the registry and deleted the key and re-added it. Still nothing. I noticed that the default value is 0, I deleted it and typed 0. Restarted Outlook, this time it worked. It seams like that is the only thing I did not do in the past. So make sure you type 0 in the DefConnectOpts value.

  • Thanks for the feedback Josh!

    This is actually one of the most hit entries out there about this particular issue (It’s surprising the number of people who run into this issue on a daily basis!)

    I’m glad I could introduce some help there through this.

    Check out some of the more recent posts as well, if you’re interested in Certification! :)


  • Reynold says:


    I have tried all of the above. I have vista home, with outlook 2003.

    1) not outlook folder under 12 there is an outlook folder under office with no RPC folder.
    2) I added the RPC folder, then the two Dword values
    3) I typed the number 0 as well under the first value

    :( No luck connecting yet, if anybody has any suggestions, I am open to hear them.

    thank you!

  • PMGNet says:

    This worked for me. I haven’t been able to connect for weeks. I rely on this connection mode heavily.

    I also had to create the RPC key and I also set the value to 0 manually for the new entry. Worked first time after that.


  • Thank you for the assistance. My tech worked on this for 3 hours yesterday. Your suggestions came up on a google search and they worked for me.

    Thanks Again for sharing this work around.



  • Thanks Mitch. I’m glad this was helpful for you (and your tech) as it was for me when I discovered this fix long ago :)

    Hundreds of people check this particular post on regularly, so I’m glad that good people are able to benefit :)

  • Luis says:

    This is great. It didnt work after setting those keys but after rebooting its now working. Thanks a lot!!

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