Steps to create an external relay connector on Microsoft Exchange 2013 and above

  • Create a front end connector with a name like “External Relay Servername”
  • Choose custom (For example, application relay)
  • All IPv4 Port 25 – Remote network settings: Fill in the IP addresses which should be able to relay
  • Security: anonymous
Get-ReceiveConnector "External Relay Servername" | Add-ADPermission -User "NT AUTHORITY\ANONYMOUS LOGON" -ExtendedRights "Ms-Exch-SMTP-Accept-Any-Recipient"

Optional Parameters

If the connector is hardly used there may be some optional parameters to be configured:

Set-ReceiveConnector -identity “Relay Connector Name” -TarpitInterval 00:00:00
Set-ReceiveConnector -identity “Relay Connector Name” -ConnectionTimeout 00:30:00
Set-ReceiveConnector -identity “Relay Connector Name” -ConnectionInactivityTimeout 00:20:00
Set-ReceiveConnector -identity “Relay Connector Name” -MaxAcknowledgementDelay 00:00:00
Set-ReceiveConnector -identity “Relay Connector Name” -MaxInboundConnection 10000
Set-ReceiveConnector -identity “Relay Connector Name” -MaxInboundConnectionPercentagePerSource 100
Set-ReceiveConnector -identity “Relay Connector Name” -MaxInboundConnectionPerSource unlimited

More Information can be found on Microsoft Technet http://technet.microsoft.com/de-de/library/bb125140(v=exchg.150).aspx