An error occurred while testing the Mail Store

So i have this weird problem, i don't know how to solve. there is one user whenever i use that account to test Exchange connectivity from anywhere it fail with the following error.

All other users work fine. Also this user is not able to load Outlook profile either due to this same reason i think.

Testing MAPI over HTTP connectivity to server mail.bayonetventures.com
MAPI over HTTP connectivity failed.

Additional Details

HTTP Response Headers:
Server: Microsoft-IIS/8.5
WWW-Authenticate: Negotiate,NTLM
request-id: ccf6e78d-0484-4621-8a42-1e8a16bd3998
X-Powered-By: ASP.NET,ARR/3.0,ASP.NET
X-FEServer: BAYVL00-122
Set-Cookie: ARRAffinity=abf4ea57de0c445171106d04c607aaad4afaa78dec8ad8d56759b61617950f88;Path=/;Domain=mail.bayonetventures.com
Date: Thu, 13 Jun 2019 10:05:37 GMT
Content-Length: 0
Elapsed Time: 6430 ms.

More Info

###### REMOTE-EXCEPTION-INFO ######

Microsoft.Exchange.Rpc.ServerUnavailableException: Connection must be re-established --->

Microsoft.Exchange.RpcClientAccess.ServerUnavailableException: Connection must be re-established ---> Microsoft.Exchange.RpcClientAccess.SessionDeadException: The primary owner logon has failed. Dropping a connection. ---> Microsoft.Exchange.Data.Storage.TooManyObjectsOpenedException: Cannot open mailbox /o=Domain/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=user name76. ---> Microsoft.Mapi.MapiExceptionSessionLimit: MapiExceptionSessionLimit: Unable to open message store. (hr=0x80040112, ec=1246) Diagnostic context: Lid: 55847 EMSMDBPOOL.EcPoolSessionDoRpc called [length=1013] Lid: 43559 EMSMDBPOOL.EcPoolSessionDoRpc returned [ec=0x0][length=318][latency=1] Lid: 52176 ClientVersion: 15.2.330.8 Lid: 50032 ServerVersion: 15.2.330.6008 Lid: 35180 Lid: 23226 --- ROP Parse Start --- Lid: 27962 ROP: ropLogon [254] Lid: 17082 ROP Error: 0x4DE Lid: 26937 Lid: 21921 StoreEc: 0x4DE Lid: 27962 ROP: ropExtendedError [250] Lid: 1494 ---- Remote Context Beg ---- Lid: 47536 Lid: 57936 dwParam: 0x20 Msg: MoMT Lid: 33360 dwParam: 0x21 Lid: 57384 StoreEc: 0x4DE Lid: 56872 dwParam: 0xFE Lid: 42712 StoreEc: 0x4DE Lid: 45434 Guid: b76da9ad-d77a-4e2e-ae86-f1378d320a08 Lid: 10786 dwParam: 0x0 Msg: 15.02.0330.008:BayVL00-122:e43e92d3-b6dc-4880-bc58-e89717fbc186 Lid: 1750 ---- Remote Context End ---- Lid: 27962 ROP: ropGetPropsSpecific [7] Lid: 26881 Lid: 21817 ROP Failure: 0x4DE Lid: 46042 StoreEc: 0x4DE Lid: 32441 Lid: 1706 StoreEc: 0x4DE Lid: 24761 Lid: 20665 StoreEc: 0x4DE Lid: 25785 Lid: 29881 StoreEc: 0x4DE at Microsoft.Mapi.MapiExceptionHelper.InternalThrowIfErrorOrWarning(String message, Int32 hresult, Boolean allowWarnings, Int32 ec, DiagnosticContext diagCtx, Exception innerException)

Can you log on to the user through OWA? Did you disable MAPI/HTTP for the single user by mistake? Run this to enable it: Set-CASMailbox adam@contoso.com -MapiHttpEnabled $true For your reference: Set-CASMailbox