Here is another issue I encountered during my Exchange 2016 migration. A hand full of users have been getting knocked out of public folders with an Event ID 9646 and they have exceed the max of 32 session objects. What the hell does that mean? Why only a few users?
Investigating Event 9646
The Monday after I migrated public folders to Microsoft’s new “Modern Public Folders” a hand full of users began calling me they were unable to access them. Their specific error was:
“Cannot expand the folder. 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.”
Last night during a maintenance window I applied my Microsoft updates and rebooted the server. Shortly after reboot I attempted to open Outlook and it failed with a server unavailable error. OWA and ECP both showed BLANK white screens. I began to panic a little because this is probably the IT guys worst nightmare! Working in the industry for over 20 years I put my panic aside and began my standard troubleshooting procedure.
Having a small shop and wearing a lot of hats here in the office tends to create a slew of challenges. Most of the time I have a ton of projects brewing so focusing on one can be difficult at times. My migration to a new Exchange 2016 server will be gradual taking about 2 to 3 weeks to complete. During the initial setup I like to let certain steps “stew” overnight to make sure there are no disruptions. I also like to be sure I have a contingency plan to undo any unforeseen issues.