When an Exchange 2010 Hub Transport Server is installed two Receive Connectors are automatically created:

• Client Receive Connector – used by end users with an SMTP client that want to send out messages. This is authenticated SMTP and the connector is using port 587 for this;
• Default Receive Connector – used to receive SMTP messages on port 25 from other Exchange Hub Transport Servers or the Edge Transport Server.

I always recommend not to change the default receive connectors with the exception of setting Anonymous Users on the Permission Groups to allow other SMTP hosts to submit messages as well.

Relaying SMTP messaging

For relaying SMTP messaging I normally recommend to use an additional Receive Connector with an additional IP address on the server. This IP address can have an easy to remember FQDN like relay.contoso.com

To create the new Receive Connector use the following command in the Exchange Management Shell:

New-ReceiveConnector –Name “Relay Connector (EXCH01)” –usage Custom –Bindings 10.19.67.33:25 –FQDN relay.contoso.com –RemoteIPRanges 10.19.67.201 –Server ServerName –PermissionGroups AnonymousUsers

This command will create a new Receive Connector, bind it to the IP address 10.19.67.33 (this should be on the network card of the server of course) and allow the IP address 10.19.67.201 to submit SMTP messages anonymously. However, only messages for recipients whose SMTP domain is an an Accepted Domain in the Exchange organization are accepted at this point. This is a default setting so the permissions on the Receive Connector have to be changed.

The ms-Ech-SMTP-Accept-Any-Recipient permission is to make sure that all submitted recipients are accepted by the Hub Transport Server. This permissions can be added with the Add-ADPermission cmdlet:

Get-ReceiveConnector –Identity “Relay Connector (EXCH01)” | Add-ADPermission -User “NT AUTHORITY\ANONYMOUS LOGON” -ExtendedRights “ms-Exch-SMTP-Accept-Any-Recipient”

If you have multiple Receive Connectors and want to check whether or not anonymous relay is enabled on any connector you can use the following command:

Get-ReceiveConnector | Get-ADPermission | where {$_.extendedrights –like “*Any-Recipient”}