Outlook slow performance and hanging

MhNashiriS hello, actually the slowness/hanging of outlook are symptoms of many causes.

You need to dig deeper into the following to try to identify the cause:-

• Outlook connectivity from end user perspective (using resource monitor to see outlook.exe connections and latency, may be use fiddler or wireshark)
• make sure there are no authentication bottlenecks with AD, by default MaxconcurrentAPI limit is 20 on exchange and AD, you can check performance monitor and check semaphore holders and semaphore waiters during the issue, if the numbers are close to 20, it might be worth it to try to increase MaxconcuurentAPI and restart netlogon service, check this link before your proceed.
• Try to further isolate the issue by minimizing the scope of the users who are seeing the issue, for example all users having same outlook version, users on specific servers or specific DAG, users with specific network connectivity, etc.
• If you have users working with online mode, try to use cached mode for a subset of the users and see if this will help.
• check for high mail queues during the issue specially if you see “outlook is trying to connect” message on outlook.
• if you have users with online archive hosted on exchange, try to disconnect the archive for some users for testing purposes and see if it will help.
• try any of the above one by one to identify which of them will help you.

finally, please let me know when you resolve the issue specially if you find it to be caused by another cause not listed above.

Good luck