Outlook 2010 Error - could not read the calendar. The connection to Microsoft Exchange is unavailable


  • When attempting to send an Email from Outlook 2010 to multiple people outside of my company, I get the following error popping up incessantly until Outlook 2010 crashes and re-starts:


    could not read the calendar. The connection to Microsoft Exchange is unavailable

    Wednesday, August 25, 2010 8:37 PM


All replies

  • Hi,

    First, try to start Outlook 2010 in safe mode (hold Ctrl key when you start Outlook) to see if it works.

    If it works in safe mode, try to disable add-ins. How to do this, see here:

    If it also not work in safe mode, try to reset the view.

    Click Start->Run and type Outlook.exe /cleanviews and click OK.

    If it still not work, I suggest you repair your .ost file. How to do this, you can refer to this article:

    Hope it helps.

    Thursday, August 26, 2010 5:42 AM
  • I have this problem a bit in reverse. I only have the issue with a couple of users when they receive an email from outside our organization that has a large group in the "to" field. I then get "could not read the calendar. The connection to MS Exchange is unavailable." I will also get a pop-up message saying "there was a problem reading one or more of your reminders." I have read many a forum posts on this and have tried everything.

    I did run Outlook in Safe Mode and the problem goes away. What Add-ins are suggested for disabling?

    Monday, January 3, 2011 9:42 PM
  • Hi Jennifer

    Did you ever find out your problem. I'm having similar problem. IF you do please let me know.

    Friday, April 8, 2011 8:52 PM
  • Hi

    Have seen LOTS of this sporadically and finally have a 100% repro sceanrio with one specific mail with ~40 external addresses in the To: line.
    The first time I click on this mail it will show the error:

    "Could not Read the Calendar. The connection to Microsoft Exchange is unavaialble. Outlook must be online or connected to complete this action"

    But - this only happens the first time I click on the mail - clicking on it subsequent times works.
    If I restart Outlook (running in online mode) it will happen again.

    It works if within File-> "Contacts" I uncheck "Display online status next to name" or "Show user photograps when avaialble"

    Network traces shows multiple MSRPC faults with Status 0x1C00001A = nca_s_fault_context_mismatch

    Have got a trace of this happening on the client, Exchange server and RPC trace, and currently escalated to MS.


    Monday, July 11, 2011 8:37 AM
  • THe way we fixed our problem, was to find the locally stored copy of the outlook file and delete it. Since everything we do is stored on the server, when they relaunch outlook it would download the server copy instead of the issue on thier computer.

    2 ways to get this result.

    1) C:\Documents and Settings\user_name\Application Data\Microsoft\Outlook\outlook.ost

        -select and delete the .ost file.


    2) go to the Control Panel, under Mail, click on Show Profiles, then select the Profile with the problem, then click Remove.

    Next time you Open Outlook, it will prompt you for your Profile Name. Name it anything and then continue and if you are online during setup, it should auto configure your account settings from the server.

    This worked for my office. hope it works for others too.

    Thursday, July 28, 2011 5:09 PM
  • Microsoft product support is investigating this issue.  Once we know the root cause and any solution I'll update the forum thread.

    As part of the investigation we are finding there might be a workaround you could use. 

    In Outlook click File, Options, Contacts.  Disable either:
    Show user photographs when available
    Display online status next to name

    Wednesday, September 7, 2011 9:18 PM
  • The correct option to uncheck is "Display online status next to name" - this one seems to resolve the issue for us. However, this is a workaround and it would be nice to have the full-functionality of Outlook 2010.

    It appears that this issue occurs when a user recieves a message/calendar item that contains a large number of external recipients. Gabriel, if you can provide us with an update on this issue, that would be great.


    Friday, October 14, 2011 8:59 PM
  • Interesting Find -

    If you are finding that the "Display online status next to name" option is grayed-out. This is caused by either one of three things.

    - Either the user is not logged into OCS
    - or the users is logged into Outlook with a different account than their OCS account
    - or their version of OCS doesn't support this feature.

    This will be helpful information to consider for those of us who are having this "Could not read calendar" issue and having to use this workaround.


    Wednesday, October 19, 2011 6:43 PM
  • Hi,

    We are running in to the same problem at the moment, is there a real fix for this issue? Not displaying the online status next to the name of recipients does resolve the issue but is, as stated, a work around not a fix!




    Thursday, November 3, 2011 12:25 PM
  • We're seeing the same issue as well.  I've also got Outlook 2010 SP1 installed.  What I've found is a better work around than disabling the presence information for contacts is to run Outlook 2010 in cached mode.  I'm only seeing the issue when Outlook is running in Online mode.

    At first I assumed it was because I had multiple entries in my Contacts list that were also in the Global Address Book but was able to recreate the issue after removing all duplicate entries from my Contacts list that were also in the GAB. 

    Cached mode is my personal preference and what I normally use but I switched to Online mode to troubleshoot this issue for one of my users.  The symptom definitely pops up with an email I received from an outside source that includes a mix of internal Exchange recipients and external contacts.  But the number isn't excessive.  There were 2 recipients in the TO: line and 13 in the CC: line.


    Tuesday, November 15, 2011 11:20 PM
  • Did anyone find a fix for this issue?  We have a couple of user who are having the same issue.

    Thursday, October 25, 2012 7:17 PM
  • Hello, We have just introduced MS Lync and not sure if this is also casuing this error but the work around of removing the ticks did seem to work.

    Was there any fix for this??

    Tuesday, November 27, 2012 2:24 PM
  • Gabriel,

       Did MS ever find a solution to this issue.   I'm using MS 7 and 2010 outlook.  I'm not using a server exchange and my PST files are on a local drive.  The "Display online status next to name" is greyed out so I cannot change it but I did uncheck the user photo line.

       I transferred my pst file to another computer and it reads the calendar perfectly every time but I need it to run on my desktop at work.  Any additional suggestions?  I hope to not have to do a complete reinstall of outlook as I have quite a few email accounts set up and would def. rather not redo those if at all possible.


    • Edited by Poolscaper Monday, December 2, 2013 6:28 AM additional lnfo
    Monday, December 2, 2013 6:26 AM
  • Below steps definitely works  but its there any permanent solution for this.

    It works if within File-> "Contacts" I unchecked "Display online status next to name" or "Show user photographs when available"

    Kindly suggest.

    Tuesday, August 4, 2015 8:02 AM