I'm a Firewall Administrator and am incharge of multiple locations. In location A, there are 80 users who use Outlook of O365 connecting to a specific domain. Similarly, in location B, there are 500 users also using Outlook of O365 connecting to same specific domain.

The issue am facing is, during the peak hours(1pm to 4 pm), in location A, where there are around 200-300 active users, the Outlook starts disconnecting. The error says - Disconnected, at the bottom right of the screen. When I do Wireshark for the Outlooks autodiscover IP, I get RST flag.

However, in location B, where there are 80 users I dont find any disconnection.

My question is, is there any concept of concurrent Outlook session through an public IP address that at a particular number of 'xyz' the Outlook wont accept new sessions and it will disconnect the user and start throwing error Disconnected. Is there any feature in Outlook that no more than 'xyz' number can connect through an IP address.

Please help!

Regards, Dipendra

  • I'm not aware of any such setting in Outlook or in Exchange Online. It's doubtful that Microsoft would implement such a setting as they have customers who connect thousands of Outlook clients from behind the same public ip address. When the problem occurs try running the Microsoft Support and Recovery Assistant for Office 365 on one of the affected computers. – joeqwerty Aug 3 '19 at 15:55
  • Also, you probably want to look at your firewall and router logs as that's where I suspect the problem is occurring. – joeqwerty Aug 3 '19 at 15:56

No such settings in Outlook or Exchange server. This issue may be related to Network issue. If you are connecting to Exchange Online, you could use SARA to troubleshoot this issue. Support and Recovery Assistant is a new tool that helps users troubleshoot and fix issues with various Office 365 apps and services. The app diagnoses common Outlook issues like account setup, connectivity issues, password issues, or Outlook stops responding or crashes.


Poor performance

Knowledge Base articles

• 2413813 How to troubleshoot issues in which Outlook 2007 or Outlook 2010 crashes or stops responding (hangs) when it's used with Office 365

• 2441551 Outlook performance is slow in the Office 365 environment

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