Hi @Lukas ,
We solved the problem.
Great to know that you've already thought of a solution and really appreciate it for your sharing!
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others." and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
[Exchange 2016 CU23 EAS error 500 ]
Issue Symptom:
There are running two Exchange 2016 servers in a DAG.
Some, not all users, get an HTTP 500 error as soon as their mobile device sends EAS requests to the server. This prevents the users from accessing their mailbox.
The only error message we find in IIS is the following:
2022-08-30 00:16:44 [xxx.xxx.xxx.xxx] POST /Microsoft-Server-ActiveSync/default.eas User=username&DeviceId=IJHHVHF2E51SRBBVNP7227LFB4&DeviceType=iPad&Cmd=Ping&CorrelationID=<empty>;&cafeReqId=70a5ec3e-bc05-428f-8a6f-19f908b3d914; 443 domain\user xxx.xxx.xxx.xxx Apple-iPad8C3/1806.72 - 500 0 0 45
2022-08-30 12:42:18 [xxx.xxx.xxx.xxx] OPTIONS /Microsoft-Server-ActiveSync/default.eas &CorrelationID=<empty>;&cafeReqId=5c56de56-402f-40d1-b2e3-fe9c2c3517d9; 443 domain\secondusername xxx.xxx.xxx Apple-iPhone14C5/1907.71 - 500 0 0 23
There are no messages in the Application log in the Event Viewer indicating EAS misbehavior.
And EAS troubleshooting was performed ,don’t had any changes.
The Solution:
By running
curl -v -k -u user@domain -H "Host:servername" --request OPTIONS https://serverip/Microsoft-Server-ActiveSync
we pointed out an XML Error in the eas backend Web.config.
After correcting this and restaring the IIS everything worked normally.
The issue was related to only some users, because we have two servers and only one iis location was misconfigured.
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