EdgeSync service cannot connect to this subscription because of error "The LDAP server is unavailable"
You configure the EdgeSynchronization in the Exchange 2010 environment but having issues with edge sync and getting following events on the HUB servers.
Log Name: Application
Source: MSExchange EdgeSync
Event ID: 1024
Task Category: Topology
Failed to connect to the Edge Transport server ADAM instance with exception The LDAP server is unavailable.. This could be caused by a failure to resolve the Edge Transport server name <> in DNS, a failure trying to connect to port 50636 on <>, network connectivity issues, an invalid certificate, or an expired subscription. Verify your network and server configuration.
When you run Test-EdgeSynchronization, you get following error also.
RunspaceId : <>
SyncStatus : Failed
UtcNow : <>
Name : <>
LeaseType : None
FailureDetail : EdgeSync service cannot connect to this subscription because of error "The LDAP server isunavailable.".
LeaseExpiryUtc : <>
LastSynchronizedUtc : <>
TransportServerStatus : Skipped
TransportConfigStatus : Skipped
AcceptedDomainStatus : Skipped
RemoteDomainStatus : Skipped
SendConnectorStatus : Skipped
MessageClassificationStatus : Skipped
RecipientStatus : Skipped
CredentialRecords : Number of credentials 0
CookieRecords : Number of cookies
Make sure TLS 1.0 is not disabled through registry on the EDGE servers, if it is then remove the TLS 1.0 registry to enable it and reboot the edge server.
Note: This is one of the cause other than blocked ports, duplicate Certificates ,DNS etc.