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Shared Mailbox + Outlook performance

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Hi everyone...


Scenario: A shared mailbox in Office 365, the size of the mailbox is approx 2.8 GB contains almost 50-60 folders and sub-folders in the inbox. I'm using outlook 2010. Accessing the each folder is slow but tolerable, but when I create a new folder in the Inbox, it gets created soon but to appear in outlook it takes almost one day. Secondly I cannot run this on online mode as we have only 2 Mbps Internet connection speed. I'm using Windows 7 OS.


Actions Taken: Uninstalled entire Microsoft office 2010 professional plus, Updated the PC with latest patches and updates and re-installed again but no joy. 

Tried troubleshooting slow outlook performance from this site: but still no joy... :(


Can anyone here help me out on this issue.


Many Thanks,




All Replies
  • Hi Gaurav9,

    I’d like to confirm your situation:

    You’ve granted your mailbox full access to this shared mailbox, and you configure your account in Outlook 2010. Therefore, this shared mailbox is displayed in Outlook.

    In addition to this KB article, you can also try the step below. Please check if this issue persists.

    1. Create a new profile in Outlook.

    2. Add your account to this profile.

    Besides, the network can also affect Outlook performance. Do other users in your organization encounter this issue? You can configure your account on another computer (on the same network environment) to test this issue.

    You can also test it on another network environment (such as home network).

    Young Yang

  • Thanks for replying Young..

    Well I have tried this in total New environment i.e is in another company which has 50 MBPS internet connection,

    Yesterday I tried to reduce the folders on top level.. since I was getting the sync issues as “Your server administrator has limited the number of items you can open simultaneously. Try closing messages you have opened or removing attachments and images from unsent messages you are composing” So I’ve created 5 folders on top level and I moved all the emails in these five folders just to confirm whether there is any issue with no. of connections. But still the problem persist.

    As you have suggested I've tried creating total new profile for outlook but it doesn't work either.

    Also the shared mailbox has full access permissions.Secondly I'm the only user who have access to this shared mailbox. Well I've tried removing the permissions for me and adding new user permission to this mailbox but no joy....

    Please help me... seems like I'm trying too many things for 0 output.

    I would like to know, is there a limit for shared mailbox – as should have 20,000 mails and not more than that? I know u might feel What a funny question??



  • Hi Gaurav,

    I appreciate your time and effort invested on this issue. For detailed information about recommended mail item limits, you can refer to the following article. The slow performance of Outlook can also be affected by the large items in the shared mailbox.

    In addition, I find you’ve granted your mailbox the full access permission to this shared mailbox. As recommended, I suggest you create a security group, and then assign the security group the full access permission to access the shared mailbox, finally add you to the group. For detailed information, please refer to:

    Young Yang

  • Hi Gaurav,

    How are things going on your side? Is there any update on this issue? We’re here to help you.

    Young Yang

  • Hi.. Young..

    Hope you are well... Sorry for the late reply...  

    Well I've read the article that you have suggested me for the limitations to number of items in the individual mailbox.. It says inbox can have 100,000 items, but in my case I have only 7 folders and in these 7 folders I have approximately 900 items in each folder which is much less than the limit (total=6500 items).

    About setting up the permissions for a distribution group.. While creating a shared mailbox I've created the distribution group and assigned the permissions.. But since the time I've had this performance issue with the outlook, I've assigned the permissions individually.. i.e directly to the user...

    This was my findings... from the Microsoft blogs: There is one tool named as OCAT

    The Microsoft Outlook Configuration Analyzer Tool (OCAT) is a program that provides a detailed report of your current Outlook profile. This report includes many parameters about your profile and highlights any known problems that it found in your profile. For any problems that are listed in the report, you are provided with a link to a Microsoft Knowledge Base (KB) article that outlines a possible fix for the problem. If you are a Help Desk professional, you can also save the report to file so that the report can be viewed in the Outlook Configuration Analyzer Tool on another client where the tool is installed.

    Here's the link:

    Really helpful tool.... Seems like the problem is solved. Even the performance of the outlook is much better than before.

    Thanks Young for your help. May be because of you I was able to find the solution for this issue.



  • Hi Gaurav,

    I am very happy to hear that this problem has been resolved. Thank you for sharing the solution with us, I am sure that other customers who encounter a similar problem will benefit from this thread.

    If you have any more questions about Office 365 in the future, please feel free to contact us by creating a new thread.

    Bourne Zhang

  • I've got a question. Would creating a security group for granting full access vs. individual user full access affect the performance and or speed of opening emails from within Outlook. I've got users complaining it takes upwards of 10-20 seconds before the email in the shared folder to open.