Failed to connect to the Edge Transport server ADAM instance with exception The LDAP server is unavailable

One of my customers had a problem with his Edge subscription, resulting in the following error:

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 <Edge_FQDN> in DNS, a failure trying to connect to port 50636 on <Edge_FQDN>, network connectivity issues, an invalid certificate, or an expired subscription.  Verify your network and server configuration.

1024

The obvious troubleshooting steps are to check firewall ports 50389 and 50636 (using a telnet client) and DNS resolution in both directions.

If both of them are ok, run Start-EdgeSynchronization. If it shows the same error, the solution is to delete and recreate the Edge subscription:

  • On one of your mailbox servers, run Get-EdgeSubscription | Remove-EdgeSubscription
  • On the Edge, run New-EdgeSubscription -FileName C:\temp\edge.xml. Repeat on other Edge servers if needed.
  • Copy the exported files to one of your Mailbox servers
  • On that Mailbox server, run New-EdgeSubscription -FileData ([byte[]]$(Get-Content -Path “C:\temp\edge.xml” -Encoding Byte -ReadCount 0)) -Site “<sitename>” => the name of the site can be found in Active Directory Sites and Services.
  • Run Start-EdgeSynchronization
  • If this still fails, it might be needed to restart the AD LDS service (and all dependent services) on the Edge servers.
  • To verify replication, run Test-EdgeSynchronization and make sure it works.

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