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Outlook takes several minutes to connect to Exchange Online (O365)

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In the last few weeks, I have come across a few companies which are having slow Outlook connection issues to Exchange Online. There are many reasons why this could occur, but I want to focus on one of them for now. This is a scenario where after opening Outlook 2010 / 2013, it takes about 2 minutes to connect to a mailbox.

If Outlook is going via a proxy server to Office 365, there is a specific issue which occurs if you have manually configured your proxy server address in IE (see screen shot below as an example). That is, Outlook thinks some IP ranges in Office 365 are internal, and therefore doesn't route the requests via the proxy server. Specifically, if you do a network monitor trace, you will see requests to a 132 and 154 range, are not routed to the proxy server.

 

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How to solve this, some options:

  1. Microsoft recommends that Outlook doesn't go via a proxy server when connecting to Office 365, instead it should have direct access to the internet (Office 365). There are many reasons why it is recommended to bypass proxy server e.g. performance.
  2. Unselect “bypass proxy server for local addresses” in IE manual proxy configuration screen. This is a quick one to test, to see if you are a victim of the issue.
  3. Have IE automatically detect proxy settings instead of manual settings (there is a larger discussion to be had on how this works than we have time for here)
  4. I haven't tested, but perhaps a PAC file will work to force the connection to the proxy for those IP ranges.

 

Note: this looks like it might be a bug, but not confirmed yet. Therefore, this issue could be resolved in a future update to Outlook. For now, you will need to go with one of the recommended fixes above. Or, post an alternate suggestion to help the community out.

Update: this was confirmed to be a bug, and Microsoft has released a hotfix and process to resolve it. This is described here: https://support.microsoft.com/kb/2916915. Personal opinion is that I still prefer the auto detect option with proxy pac file though as a solution.

Comments

  • Anonymous
    December 16, 2013
    FYI, have been in discussions with Microsoft on this today.  Extract from results of our case : The behavior is considered by design and it is addressed in Critical Design Change Request. We have scheduled a fix for Outlook 2010 in February 2014 cumulative update. A fix for Outlook 2013 will also follow, but Outlook 2007 will not be addressed because it is in Extended Support. There are two possible workarounds for this behavior: • First, and I wouldn’t recommend it, is to allow Direct traffic through the Firewall to Office 365. The advantage of this approach is that it will be done centralized and it will impact everyone immediately. Information about the O365 IP addresses onlinehelp.microsoft.com/.../hh373144.aspx There are two downsides to this behavior:   o first you need to maintain the Firewall exceptions as IP from O365 server can change without notice   o second, winhttp traffic may go through both proxy and direct and this can cause unforeseen behaviors. • The second approach is to use a proxy pac instead of manually setting in the proxy and the exceptions. The advantage is that you will have centralized method to control how winhttp traffic goes and the issue will not be experienced anymore.  However, you may have some challenges with deployment and connectivity topology so a single pac might not be fit.  Yet you can configure proxy pac files for each site requirements and use an IIS server to store it.

  • Anonymous
    January 05, 2014
    Thanks for giving feedback on this Dyanne, much appreciated.

  • Anonymous
    February 23, 2014
    The comment has been removed

  • Anonymous
    February 26, 2014
    Excellent article, thanks! Its early days but a quick test this morning shows the issue is still present with Office 2013 SP1.

  • Anonymous
    April 28, 2014
    The comment has been removed

  • Anonymous
    June 13, 2014
    This is the following fix for the Outlook proxy workaround support.microsoft.com/.../2916915

  • Anonymous
    June 15, 2014
    Fix for Outlook 2013: support.microsoft.com/.../2878323

  • Anonymous
    June 16, 2014
    Hotfix works for me on Windows 8.1 with Office 2013, Win 7 with Office 2010 does not work after fix.

  • Anonymous
    August 10, 2014
    Here is a KB article which describes the fix process support.microsoft.com/.../2916915

  • Anonymous
    October 09, 2014
    As per the infromation above for an outlook 2010 SP2 client I had to install the below hotfixes outlook2010-kb2878254-fullfile-x86-glb Windows6.1-KB2916915-x64 I also had to create the below registry Key HKEY_CURRENT_USERSoftwareMicrosoftOffice14.0OutlookRPCEnableForceHttpProxy value 1 However this is only good from computers on premesis, as soon as a laptop user goes offline they are forced to use a proxy which they cannot, this result in ZERO connection so for most of our user base this has just shifted the problem. I am trying to figure out what we can do to fix this 4:20 connection issue for all users no matter how they connect.

  • Anonymous
    November 12, 2014
    We've the same problem with proxy and with users accessing Outlook from home. Enabling this causes no connectivity to Exchange: HKEY_CURRENT_USERSoftwareMicrosoftOffice14.0OutlookRPCEnableForceHttpProxy value 1 @MT - did you find any fix for this? Thanks

  • Anonymous
    March 26, 2015
    Same problem here too with proxy and accessing outlook away from office. MT , Runiuksp did you ever find a fix for this?

  • Anonymous
    September 21, 2015
    Dear Microsoft, I am paying you every year for our Action Pack and also for some accounts on your Office365 platform. However, connecting to your servers is taking 1990's style delays. All my websites and other internet resources are OK, but going to Office 365 portal, or letting Outlook connect to the Office365 servers to fetch mail is taking unacceptable times, in terms of 30+ minutes! I am not sure if I can still take your services serious... and I hope for a good solution. It also doesnt make any sense to me that these forums mostly dont include any official response from your side Microsoft. I would fix that too, maybe just allocate a few of your ten thousands of employees to keep an eye on the questions asked. Thanks! JP