exchange hybrid endpoint not working

Question

dears,

i need your expertise with the below:

exchahge hcw was configured successfully and i was able to migrate mailboxes without any problem
recentlry, when i do it i receive this error: the connection to the server could not be completed

mrs is enabled, tried to disable and reenable with iis reset. nothing changed
wsauth is true too

ews and autodiscover using remote connectivity are working too.

https://webmail.com/ews/exchange.asmx working too internally and externally
https:,//webmail.com/ews/mrsproxy.svc returning error 503 internally and externally

test-migrationserveravailability fails with the below:

RunspaceId : 401fd068-6876-4ad5-995a-816d24ff18ec
Result : Failed
Message : The ExchangeRemote endpoint settings could not be determined from the autodiscover response. No
MRSProxy was found running at 'nhwebmail..com.lb'.
ConnectionSettings :
SupportsCutover : False
ErrorDetail : internal error:Microsoft.Exchange.Migration.MigrationRemoteEndpointSettingsCouldNotBeAutodiscovere
dException: The ExchangeRemote endpoint settings could not be determined from the autodiscover
response. No MRSProxy was found running at 'nhwebmail.itg.com.lb'. --->
Microsoft.Exchange.Migration.MigrationServerConnectionFailedException: The connection to the
server 'nhwebmail.i.com.lb' could not be completed. --->
Microsoft.Exchange.MailboxReplicationService.RemoteTransientException: The call to
'https://nhwebmail.itg.com.lb/EWS/mrsproxy.svc' timed out. Error details: The request channel
timed out attempting to send after 00:00:00.0003137. Increase the timeout value passed to the
call to Request or increase the SendTimeout value on the Binding. The time allotted to this
operation may have been a portion of a longer timeout. --> The HTTP request to
'https://nhwebmail..com.lb/EWS/mrsproxy.svc' has exceeded the allotted timeout of
00:00:00.0003137. The time allotted to this operation may have been a portion of a longer
timeout. ---> Microsoft.Exchange.MailboxReplicationService.RemotePermanentException: The request
channel timed out attempting to send after 00:00:00.0003137. Increase the timeout value passed to
the call to Request or increase the SendTimeout value on the Binding. The time allotted to this
operation may have been a portion of a longer timeout. --->
Microsoft.Exchange.MailboxReplicationService.RemotePermanentException: The HTTP request to
'https://nhwebmail.com.lb/EWS/mrsproxy.svc' has exceeded the allotted timeout of
00:00:00.0003137. The time allotted to this operation may have been a portion of a longer timeout.
--- End of inner exception stack trace ---
--- End of inner exception stack trace ---
at Microsoft.Exchange.MailboxReplicationService.MailboxReplicationServiceFault.<>c__DisplayClas
s1.<ReconstructAndThrow>b__0()
at Microsoft.Exchange.MailboxReplicationService.ExecutionContext.Execute(Action operation)
at Microsoft.Exchange.MailboxReplicationService.MailboxReplicationServiceFault.ReconstructAndTh
row(String serverName, VersionInformation serverVersion)
at Microsoft.Exchange.MailboxReplicationService.WcfClientWithFaultHandling2.<>c__DisplayClass1 .<CallService>b__0() at Microsoft.Exchange.Net.WcfClientBase1.CallService(Action serviceCall, String context)
at
Microsoft.Exchange.MailboxReplicationService.WcfClientWithFaultHandling`2.CallService(Action
serviceCall, String context)
at Microsoft.Exchange.Migration.MigrationExchangeProxyRpcClient.CanConnectToMrsProxy(Fqdn
serverName, Guid mbxGuid, NetworkCredential credentials, LocalizedException& error)
--- End of inner exception stack trace ---
at Microsoft.Exchange.Migration.DataAccessLayer.ExchangeRemoteMoveEndpoint.VerifyConnectivity()
at Microsoft.Exchange.Management.Migration.TestMigrationServerAvailability.InternalProcessEndpo
int(Boolean fromAutoDiscover)
--- End of inner exception stack trace ---
IsValid : True
Identity :
ObjectState : New

i have one cas and one mbx 2013 servers.
in both webconfig files there is no data import number of connections neither mrs proxy connections values. i dont know if this is the issue

i have been stuck with the above
your experience is highly appreciated

thanks

Answer 1

The issue is related to the back-end mailbox database server not having SSL assigned to IIS. The same public SSL is required when the CAS server connects to the backend mailbox database server. I had the same problem, and its documented on this blog https://blog.shiraj.com/2023/08/the-remote-server-returned-an-error-503-server-unavailable-when-moving-mailboxes-to-exchange-online/