As of probably a few months ago, I am getting random clients randomly disconnected from my Exchange 2013. Outlook 2010 will state that it is Trying To Connect and sits there, sometimes for a few moments, and other times for an hour or longer. This affects AD connected computers and users directly on the network as well as non-AD computers and users off the network.
The certificate is correct. When the client loses connectivity, if I remote into their machine, they can successfully ping the exchange server with no issues. Holding down CTRL and right clicking the Outlook icon on the sys tray, I am able to test the AutoDiscover and config successfully. The connection information, though, states that it is trying to connect.
I have removed profiles and recreated them. However in some instances, this does not work and the client does not successfully log onto the Exchange server, i.e. in the auto setup, it has a check for boxes 1 and 2, and then tosses an error that the exchange server is unavailable.
The local network is pretty flat. I am on the same switch as the servers. I have had this happen to me as well. The network itself goes from a Cisco router to a Fortigate firewall/switch, from there it goes to the server switch and the switches on the individual floors.
The Exchange Server is Exchange 2013, running on a Hyper-V Windows Server 2012 R2 Standard. This Hyper-V machine is hosted on a HP Proliant server, 64Gb of RAM, 3TB of storage, and it is only running that one Hyper-V machine. The Hyper-V setup itself has plenty of processors and 3/4 of the total RAM assigned to it, but it never really uses that much at all.
I have tried removing the fortigate as that is the new piece of hardware, just to make sure it wasnt that being goofy, and the problem continues, and yes even with that removed, I was able to ping the server, the autodiscover test completed perfectly, but the user still could not connect. Recreating the profile eventually fixed it, to only have it show up again the next day.