Symptoms
When you migrate Microsoft Exchange Server 2010 mailboxes to Exchange Online in a hybrid environment that has Microsoft Exchange Server 2016 installed, the migration fails randomly and returns the following error message:
Transient error CommunicationErrorTransientException has occurred. The system will retry
Additionally, you may receive the following TransientException error message:
Timestamp: DateTimeFailureType: CommunicationErrorTransientExceptionFailureHash: ea66FailureCode: -2146233088MapiLowLevelError: 0FailureSide: SourceFailureSideInt: 1ExceptionTypes: {Exchange, Transient}ExceptionTypesInt: {1, 2}Message: The call to 'https://mail.DomainName.com/EWS/mrsproxy.svc ServerName.DomainName.com (x.x.x.x caps:AFFFBF7FFFFFCB07FFFF)' failed. Error details: Exception from HRESULT: <0x80D5DC38>. --> Exception from HRESULT: <0x80D5DC38>.
Note In the "Error details" section of this message, the "0x80D5DC38" HRESULT hex code represents the actual hex code that is generated.
Resolution
To fix this issue, install cumulative update 5 for Exchange Server 2016.
