Have you tried restarting the server after ending any existing migrations/retrievals? I'm thinking something might be hung up and flushing out the ongoing ones might help. You can also increase the IMAP/POP/EWS retrieval logging (whichever you're using primarily) and use those logs to look for exceptions. The log detail levels can be increased in Manage>Troubleshooting>Options, then you can review those logs in Manage>Troubleshooting>View Logs as a system administrator. 

Hi Daniel. We ran into this issue with one of our clients not receiving email from outside their company. On webmail, try going to your contacts and see if you get an error message in the lower right corner of your screen.

Hello,

Well even if i want do add a new retrieval task it wont let me i will allways gett the  "Unable to connect with the credentials supplied." (if i test with tcpviewer i will see that the connection isnt even done).

Exception: System.AggregateException: One or more errors occurred. (Exchange Server doesn't support the requested version.)

[2024.08.05]  ---> Microsoft.Exchange.WebServices.Data.ServiceVersionException: Exchange Server doesn't support the requested version.

[2024.08.05]    at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ProcessEwsHttpException(EwsHttpException httpException)

[2024.08.05]    at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.GetEwsHttpWebResponse(IEwsHttpWebRequest request)

[2024.08.05]    at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ValidateAndEmitRequest(CancellationToken token)

[2024.08.05]    at Microsoft.Exchange.WebServices.Data.SimpleServiceRequestBase.InternalExecuteAsync(CancellationToken token)

[2024.08.05]    --- End of inner exception stack trace ---

[2024.08.05]    at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)

[2024.08.05]    at System.Threading.Tasks.Task`1.get_Result()

[2024.08.05]    at Microsoft.Exchange.WebServices.Data.SimpleServiceRequestBase.InternalExecute()

[2024.08.05]    at Microsoft.Exchange.WebServices.Data.MultiResponseServiceRequest`1.Execute()

[2024.08.05]    at Microsoft.Exchange.WebServices.Data.ExchangeService.InternalFindFolders(IEnumerable`1 parentFolderIds, SearchFilter searchFilter, FolderView view, ServiceErrorHandling errorHandlingMode)

[2024.08.05]    at Microsoft.Exchange.WebServices.Data.ExchangeService.FindFolders(FolderId parentFolderId, FolderView view)

[2024.08.05]    at Microsoft.Exchange.WebServices.Data.ExchangeService.FindFolders(WellKnownFolderName parentFolderName, FolderView view)

[2024.08.05]    at MailService.RelayServer.MessageRetrieval.Exchange.ExchangeClient.TestConnection()

That looks like a different issue. Our issue was with an invalid contact. Although, it had worked fine before the upgrade.

well i am talking about the email retrieval (migration in cennection settings)

The error you posted (referenced below) seems to hint at an unsupported Exchange server version: 

If you don't already have a ticket open on this we should be able to help investigate further from there. 

Hello,

I did a rollback to 8930 yesterday, Email retrieval is working again so for me this means -> complete migration proccess and only upgrade after completion.

I suggest sticking with the 8930 a little longer...

I see too many complaints/bugs posted here regarding the "new releases"...

I checked in with development on this and they said we target Exchange 2010+, and that no new properties have been added that should affect import and so they'll need to debug this further. I'm going to get a ticket started for this so we can help get to the bottom of it!