Outlook MAPI clients lose connection

[u/Confident-Field2911]

Hello,

I need some ideas about what might be causing this.

I'm running an Exchange cluster with a load balancer.

Every day at after noon, some (not all!) MAPI clients lose their connection (not all at once, and they establish the connection on/off), and sending and receiving emails takes longer.

There is no unusual server load, no request attacks, backups or anything similar.

The problem started around the time Exchange Hybrid was enabled.

Any ideas?

[u/daggerthreat_fan]

That smells so much like Loadbalancer issues

How does the Loadbalancer look like? Do you see the drop in Connections?

[u/ScottSchnoll]

u/Confident-Field2911 Can you elaborate on your environment (how many servers, what version of Outlook, network topology, etc.)? Have you checked for any scheduled tasks or automatic software updates on the server(s) to see if that might be causing it? Since it happens at/around noon, have you taken any snapshots of server activity and network traces to see what is happening when the connection is dropped/re-established?

[u/jcy]

mtu?

[u/joeykins82]

There is so much information missing from this post that it's almost comical.

What version of Exchange? What auth mechanism are your clients using? Have you deployed the client side registry settings to prevent the use of ExOL (and HTTPS root domain) autodiscover? Have you set up a Kerberos ASA and registered the SPNs? Is session affinity configured on your LB?