none
Are there concurrent connection limits for a user connecting to Exchange using Outlook using Outlook Anywhere? RRS feed

  • Question

  • I have a client that has an Exchange 2013 server with all of their users either connecting via OWA or Outlook 2013 using the now default Outlook Anywhere connection. (RPC over HTTP?)

    Basically, there seems to be a cap on how many times a user can log into Outlook from 1 location.

    My client has multiple sites, all VPN connecting to his Office where his Exchange server resides.  All PCs are on the domain.  Currently, only 2 of these locations have clients that use Outlook.  The other locations are currently using OWA, though when they receive the new PCs, everyone will be using Outlook.

    One of these locations (the location I'm having the issue with), has 5 computers that all log in as the same user.  It's very easy to duplicate.  I start the first 3 PCs Outlooks, and they all connect, I start the 4th one, and it shows disconnected.  I close one of the connected Outlooks, and if I restart the Outlook on the disconnected PC, it now will connect.

    I thought this issue was resolved when I disconnected all users at the site, and one at a time, removed the outlook profiles from each of the machines and setup the account again.  I was able to connect all 5 PCs at that time, and restart them.  Now, it appears like the same issue or some semblance of it is back.

    Outlook is set to "Connect to Microsoft Exchange using HTTP"

    I'm looking for guidance.  I'm considering using a shared e-mail account and setting up each of the users with their own account, but that'll involve them purchasing licenses for additional exchange accounts.  I just have a feeling that this could be a easy fix, if I knew where to look.

    Tuesday, November 24, 2015 4:46 PM

Answers

  • If it were me. I would set Maximum Allowed Sessions Per User to 64. Restart the IS service ( after hours of course) and test.

    If you are using a DAG, then even better. Activate the databases to another server, make the change on the passive node, and activate the database of this mailbox back and test.

    As far as sessions that are being used now, generally its 4 or 5 per open client, but that can up if there are Outlook Add-ins or the Outlook client is caching shared mailboxes.

    Get-StoreUsageStatistics

    https://technet.microsoft.com/en-us/library/dd876852(v=exchg.160).aspx

    Running the above command for that mailbox may help determine total sessions, but only if its in the top 25.

    You could also use netstat or TCPView to get a rough estimate:

    https://technet.microsoft.com/en-us/sysinternals/tcpview.aspx

    Unfortunately, Get-LogonStatistics doesnt work in 2013.


    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.

    Tuesday, November 24, 2015 8:21 PM
    Moderator

All replies

  • Sounds like you either hitting throttling or the max allowed sessions on the store.

    IF you are you would see errors in the app log like error 9646.

    Options:

    Raise the maximum allowed sessions per store:( works in 2013 AFAIK)

    https://technet.microsoft.com/en-us/library/ff477612(v=exchg.141).aspx

    Exchange Store Limits

    and/or

    Create a seperate throttling policy for those users for

    https://technet.microsoft.com/EN-US/library/jj863577(v=exchg.150).aspx

    The value you are probably need to raise is:RCAMaxConcurrency

    https://technet.microsoft.com/en-us/library/dd297964(v=exchg.141).aspx


    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.

    Tuesday, November 24, 2015 5:03 PM
    Moderator
  • I searched the Application Logs for Errors and found of 9646 IDs for MSExchangeIS.  The contents of the event show the following:

    Mapi session /o=????????/ou=First Administrator Group/cn=Recipients/cn=??????? with client type MoMT exceeded the maximum of 32 objects of type Session.

    In your first link, I found reference to "MAPI on the Middle Tier (MoMT)" who's "Default number of user sessions per server" is 32.  I think this is what needs modified.

    The document shows the way to adjust default session limits is by editing the registry.  I can set a "Maximum Allowed Sessions Per User", "Maximum Allowed Service Sessions Per User", a "Maximum Allowed Exchange Sessions Per Service", or/and a "Maximum Allowed Concurrent Exchange Sessions Per Service" value.  It also allows me to disable session limits.

    This is confusing to me, because I don't know what the current value for either of these are.  So, what happens if I pick a value based on incomplete information.  If one of them was to change the number of users connected via this MoMT, I know it's currently hitting the ceiling at 32, so I could try 64 and see if the errors show up again after connecting a bunch of users, but I'm not seeing that.

    As is, if I change, say, the "Maximum allowed Sessions Per User" to 64, it's going to have a more global effect than my adjusting just the MoMT session limit.  Also, I'd prefer being able to type a command or look up a value, change it, and confirm that it changed.

    Knowing what the specific error message is in the application log, do you have any advice on the specific fix?

    Tuesday, November 24, 2015 7:59 PM
  • If it were me. I would set Maximum Allowed Sessions Per User to 64. Restart the IS service ( after hours of course) and test.

    If you are using a DAG, then even better. Activate the databases to another server, make the change on the passive node, and activate the database of this mailbox back and test.

    As far as sessions that are being used now, generally its 4 or 5 per open client, but that can up if there are Outlook Add-ins or the Outlook client is caching shared mailboxes.

    Get-StoreUsageStatistics

    https://technet.microsoft.com/en-us/library/dd876852(v=exchg.160).aspx

    Running the above command for that mailbox may help determine total sessions, but only if its in the top 25.

    You could also use netstat or TCPView to get a rough estimate:

    https://technet.microsoft.com/en-us/sysinternals/tcpview.aspx

    Unfortunately, Get-LogonStatistics doesnt work in 2013.


    Twitter!: Please Note: My Posts are provided “AS IS” without warranty of any kind, either expressed or implied.

    Tuesday, November 24, 2015 8:21 PM
    Moderator
  • Alright, I made the registry change and scheduled a restart.  I will be following up on this tomorrow.
    Tuesday, November 24, 2015 9:45 PM
  • Hi,

    Sessions represent the connections used by services and client applications, such as Microsoft Outlook, to connect to the Exchange store. Services and clients can have multiple sessions at a particular time.

    The error 9646 indicates Mapi session exceeded the maximum value.

    Please have a look at the following article:

    https://support.microsoft.com/en-us/kb/2742012

    You can refer to the below link to resolve this error:

    In addiction, I have found a similar thread for your reference:

    https://social.technet.microsoft.com/Forums/exchange/en-US/91922b60-38b7-4af3-ba13-3b44949cc9f7/event-9646-msexchangeis-mapi-session-exceeded-the-maximum-exchange-2010-sp1-w-update-roll-up-2?forum=exchange2010

    Regards,                                                                                                              

    David 


    Wednesday, November 25, 2015 2:03 AM
    Moderator