How to forward mail to an external email address in Exchange Server 2007

From http://exchangepedia.com/blog/2008/02/how-to-forward-mail-to-external-email.html we read:
In Exchange Server 2003, mail for a recipient can be forwarded to an alternate recipient by modifying the recipient's Delivery Options in ADUC | recipient -> properties | Exchange General tab.

If you need to forward mail to an external email address, you cannot simply type the address in Delivery Options. A (mail-enabled) Contact needs to be created in AD first, and Delivery Options modified to point to the Contact.

Exchange Server 2007: In Exchange Server 2007, these tasks remain the same. However, instead of using ADUC to accomplish them, you use the EMC or the shell (aka "EMS"). The new term for a Contact is MailContact.

1 To create a MailContact using the Exchange Management Console:

1. Expand Recipeint Configuration | Mail Contact
2. In the Action pane, click New Mail Contact
3. To create a new Contact object, leave the default (New Contact) selected | click Next
4. Type First name, Last name
5. Click Edit to add the external email address
6. Click New to complete creation of new MailContact

To create a new MailContact using the Exchange Management Shell:

New-MailContact -Name "Foo User" -ExternalEmailAddress "foo@externaldomain.com
Next, we set the recipient's Delivery Options to deliver to the alternate recipient.

2 To forward mail for a recipient to the MailContact using the Exchange Management Console:

1. Expand Recipeint Configuration | Mailbox | select mailbox | properties | Mail Flow Settings tab | Delivery Options
2. Under Forwarding address, select the Forward to checkbox
3. Click Browse to select the MailContact
4. Optional: If a copy of the message needs to be delivered to both the external recipient and the original recipient's mailbox, select the Deliver message to both forwarding address and mailbox
5. Click OK to close Delivery Options properties
6. Click OK to close recipient's properties

Using the Exchange Management Shell:

Set-Mailbox "Joe Adams" -ForwardingAddress "foo@externaldomain.com"
To deliver a copy to the mailbox (in addition to the external email address - equivalent of step 4 above):

Set-Mailbox "Joe Adams" -ForwardingAddress "foo@externaldomain.com" -DeliverToMailboxAndForward $true
To get a list of mailboxes with forwarding enabled:

Get-Mailbox | where {$_.ForwardingAddress -ne $null} | ft name,forwardingaddress

Automatic forwarding and Remote Domains

Remote Domains are a bunch of settings, such as message formats, character sets, and OOFs, for messages sent to particular remote domains. The default Remote Domain setting applies to address space * - that is, all remote domains for which an explicit Remote Domain setting does not exist.
However, this setting only applies to client-side forwarding. For instance, if a user creates a rule in Microsoft Outlook to automatically forward mail to an external email address, the default setting does not allow it. To enable automatic client-side forwarding of mail to external addresses, select the Allow automatic forward checkbox in a remote domain's properties | Format of original message sent as attachment to journal report tab (Yes, the tab is mislabeled. It is the "Message Formats" tab... :).

Server-side forwarding setup by an administrator is not impacted by this setting.