Outlook Unable To Connect To Exchange –Default Gateway Not Found

When doing some recent customer work for Exchange 2013, I ran into an annoying issue in one of my labs.  Outlook 2013 refused to connect to Exchange 2013.   A witch hunt then ensued to ensure that all of my Outlook Anywhere, Autodiscover and authentication settings were correct.  Well it turns out that they were, and this was just a client side issue.  Legacy IIS permissions when coexisting with Exchange 2013 are covered here for example. 

The symptom was that Outlook would not connect using an existing profile, and was unable to create a net new profile.  When creating a new profile the error received was “The action cannot be completed.  The connection to Microsoft Exchange is unavailable.  Your Network Adapter does not have a default gateway”. 

Since this entire lab exists on a single flat subnet ( ) I foolishly, ignored the default gateway bit of the error message and focussed on client connectivity.   Why would it want a default gateway when all machines are on a single subnet, the network is a private Hyper-V switch and all machines resolve names perfectly……

Let’s look at what was going on and then remediate manually and how to automate the fix. 

Running Outlook  Auto Account Setup

Trying to create a new Outlook 2013 profile with pre Outlook 2013 SP1 and then Outlook 2013 SP1 both resulted in the same issue.

Firing up Outlook initiated the Auto Account setup.  As expected we hit up AD to get the SMTP address and then query AD for the Autodiscover SCP endpoints.  For details on Autodiscover please see this post.   

Creating New Outlook 2013 Profile - Auto Account Setup

All normal so far.  We issued the LDAP query to AD, did the Autodiscover SCP query, and start to process the Autodiscover response. 

Creating New Outlook 2013 Profile - Searching For Settings...

Then the wheels fall off the wagon……

The action cannot be completed.  The connection to Microsoft Exchange is unavailable.  Your Network Adapter does not have a default gateway

Clicking OK, shows the below dialogue box. 

Mailbox GUID Displayed in Exchange Server Name Field

Couple of things to mention about the content of the above window.  Note that the Exchange server field does not state the name of any of the Exchange servers.  Is this something to be worried about? The answer is no.  This was a deliberate design change in Exchange 2013 to provide a single consistent identity that Outlook could store.  The intent was to minimise the occurrences of “Your administrator has made a change that requires you to restart Outlook”.  We can talk more about that with MAPI/HTTP. 

You will note that the information specified in the Exchange server name is the ExchangeGUID of the mailbox.  This can be seen below:

Get-Mailbox Administrator | Select Name, *GUID*

Checking Mailbox's ExchangeGUID

You will note that the ExchangeGUID does not show up in the ADDS cmdlet:

Get-ADUser Administrator | Select Name, *GUID*

ExchangeGUID Is Not Present Within ADDS Get-ADUser Cmdlet

Going back to the error screen again…..

Clicking Check Name again, just shows the previous error – The connection to Microsoft Exchange is unavailable.  Your network does not have a default gateway.

What’s up with this? 

Correcting The Issue By Disabling Outlook Connection Optimisation

In this case we are using a pretty rare scenario.  All of these test machines exist on an isolated segment with no other network access whatsoever.  Typical client machines have a default gateway configured to allow IP traffic to flow correctly in the environment.  Outlook 2007 will typically look for a machine to have a default gateway set so they can perform some more advanced connection optimisation compared to Outlook 2003.  In this case it this which is getting in the way.  As described in KB 913843, this is disabled in the registry.  The registry keys and values to set will depend upon the version of Outlook that you have installed.    The registry keys are:

Outlook Version Registry Path
2007 HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\RPC
2010 HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\RPC
2013 HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\RPC

Which contains a  REG_DWORD called  DefConnectOpts  = 0

Note that the RPC key may not currently exist.  If it does not you can manually create it or use the automated solution below in this post. 


This registry data disables the new Outlook 2007 connection logic and forces Outlook 2007 to use the same connection logic available in Outlook 2003.  One check that gets disabled is  the step to validate if a default gateway is present. 

Please note that there are multiple reasons Outlook 2013 may not want to connect to Exchange 2013.  This is just one of them.  A couple of the other recent ones that I have see are:

KB 2264398 Outlook Unable to perform a Check Name or connect to an Exchange mailbox may get these errors:

KB 2934750 Outlook 2013 cannot connect after an Exchange Server 2010 mailbox is moved to Exchange Server 2013



If you want to automate this via a script, logon script or just don’t want to have to browse the registry, we can use the venerable reg.exe tool. 


To Set The Outlook 2013 DefConnectOpts  Registry Value

Reg.exe Add HKEY_CURRENT_User\Software\Microsoft\Office\15.0\Outlook\RPC  /T REG_DWORD  /V DefConnectOpts  /D "0"

To Check For The Outlook 2013 DefConnectOpts  Registry Value

Reg.exe Query HKEY_CURRENT_User\Software\Microsoft\Office\15.0\Outlook\RPC /V DefConnectOpts


Funnily enough, after the fact I remembered that I’d seen this previously, about 5 years ago.  Those who forget the past certainly do repeat the same mistakes!




Comments (26)
  1. anonymouscommenter says:

    I also stumbled across this many times with outlook 2010 I just remember to use d gateway:)
    but thanks for the dtailed explanation, didn’t know about reg key
    always interesting here

  2. anonymouscommenter says:

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  3. anonymouscommenter says:

    Pingback from How to Detect and Stop an Outside User from Stealing Your WiFi – iForeignAffairs

  4. anonymouscommenter says:

    I tried your solution with no luck, I still get the error. I am not sure what else to try

  5. anonymouscommenter says:

    I try this option, but not result.
    I create new acoutn windows user, when I run outlook, tape my mail and password, and work.
    While work? I don’t know,

  6. anonymouscommenter says:

    @Krzystof When you make changes to registry, you need to restart your machine to take affect

  7. IIRC this one kicks in on the fly Duke. Happy to get feedback on that either way please!

    Other ones like changing TCP/IP require a restart as that service only initialises at boot time.


  8. anonymouscommenter says:

    This happened to a client in my environment sort of randomly (well, I was making some CAS array changes recently). I tried a bunch of other things, but this fix worked perfectly! Thanks Rhoderick!

  9. anonymouscommenter says:

    Here is a fix… You are probably trying to connect to Exchange that does not have a valid SSL cert. When you add a profile thru Control Panel/Mail you will see that you get an "x" in the SSL cert… All you need to do is import that certificate as a "Local
    User" and you will see that Outlook connects instantly right after that!

  10. Friends don’t let friends use self signed certificates or invalid certificates. That is a fudge for an SSL issue, but not really a fix for this.


  11. anonymouscommenter says:

    I’m having a similar issue, but I don’t use exchange server. Just good ol’ normal connections. I did not have this problem previously, but bought a new lap top and downloaded Office 365. Outlook appeared to install correctly and I got all my email address
    set up then all of a sudden I now get this error message when I try and run outlook; "The connection ot Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action".

  12. anonymouscommenter says:

    Thanks. I had a similar environment and the same problem "Default Gateway not found". Your solution worked.

  13. anonymouscommenter says:

    Very good article ! You’re my master !

  14. anonymouscommenter says:

    i have same problem but your solution doesn’t work, i found the DefConnetOpts value is there. please your help

  15. anonymouscommenter says:

    Does anyone know what the Outlook client actually is looking for throgh the gateway? "Connection Optimization" means what?

  16. anonymouscommenter says:


  17. anonymouscommenter says:


  18. anonymouscommenter says:

    Experienced the same issue today when the default gateway was left blank. Worked out though that if we set a random IP address as the default gateway (one not assigned to anything at all) the Outlook client is happy and connects to Exchange without the

  19. anonymouscommenter says:

    Connection state may be set to use HTTP, so looking for the gateway for the connectivity. Whats bound to the NIC?

  20. anonymouscommenter says:

    tried RPC registry fix, but I still get the same error message after restarting outlook and exchange. any other suggestions

  21. anonymouscommenter says:

    The year 2015 is almost done, and 2016 is upon us! As in previous years , I thought it would be interesting

  22. anonymouscommenter says:

    Doesn’t work 4 me on Win 10 et Office 2007… How to download certificate from a server who might kindly help? Or how to set a défaut gateway random – I’ve heard that it might help also.. Please kindly aide svp.

  23. prashanth says:

    Please check the subnet configured in TCP/IP setting, also ensure all ports are opened in firewall and all exchange servers are listed HOSTS file. this will fix the issue.

    1. Agree with checking the TCP configuration! Firewall needs to be opened to allow traffic from clients, but there should be no scenario where hosts files are required to access Exchange (apart from testing).


  24. Ankur Sharma says:

    i am facing issue with outlook users, while i connect through VPN then outlook works fine, but without VPN it cannot works (connect with exchange server).
    could you please help on this…

  25. Bruno Lopes says:

    Great article, Rhoderick. Thank you!

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