The Exchange administrator can use a Remote Domain to control many aspects of email globally. Along with controlling the email format (HTML or RTF) used on email sent to Internet addresses, the administrator can also configure Exchange to allow (or block) Out of Office messages, automatic replies and forwards, and read or delivery receipts or non-delivery report to the domain.

The administrator can configure multiple remote domains as to allow some actions to specific domains while blocking other domains. For example, the administrator can block mail sent by rules to forward mail to Hotmail or Gmail accounts while allowing automatic forwards to a client's domain.

The remote domain feature is accessed through the Exchange Management Console Organization Configuration > Hub Transport > Remote Domains or using the following cmdlets.

To get a list of all remote domains where the parameter (TNEF, in this example) is disabled:
Get-RemoteDomain | Where {$_.TNEFEnabled -eq $false}

To create a new remote domain, enter a DomainName and a friendly name:
New-RemoteDomain -DomainName thedomain.com -Name thedomain

To enable a parameter, in this example we are enabling TNEF to the remote domain named "thedomain":
Set-RemoteDomain -Identity thedomain -TNEFEnabled $true

To disable TNEF on the default domain, use
Set-RemoteDomain -Identity Default -TNEFEnabled $false

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Commonly used Remote Domain Parameters

Below are the most commonly used RemoteDomain settings. As in the examples above, use the parameter and value in the cmdlet. You can use multiple parameters if necessary.
Set-RemoteDomain -Identity gmail -TNEFEnabled $false -AutoReplyEnabled $true -NDREnabled $false

For complete list, see Set-RemoteDomain (TechNet)