OS X Server (Mountain Lion) instructions
- 
	
- In Server.app, go to Users and select a user. 
	
- Click the gear icon (or Control-click the user name) and choose "Edit Mail Options..." 
	
- From the "Mail should be:" pop-up menu, select "forwarded". 
	
- Enter the forwarding email address in the "to email address:" field. 

Lion Server instructions
Enabling auto-forwarding for an account
To enable an account for auto-forwarding, run the following commands in Terminal on the server. The first command puts you in interactive mode.

sudo serveradmin command
mail:command = setAutoForward
mail:userID = (the_users_shortname)
mail:fwdAddress = (the_emailaddress_to_forward_to_)
Press Control-D to complete the command.

After completing the command by pressing Control-D, it should return the userID, GUID and the newly set auto-forward address. For example:

mail:userID = " mailuser1"

mail:userGUID = "A961DAFE-2FE5-4EEC-A2CB-CB6511E9B28D"

mail:fwdAddress = "my-user-ID@example.com"



If the user does not exist, the following message will be returned:

mail:error = "user not found"
To disable auto-forwarding for an account
Use the same commands as above, but with an empty address value:

sudo serveradmin command

mail:command = setAutoForward

mail:userID = mailuser1

mail:fwdAddress = ""
Press Control-D to complete the command.
The response will be the same as above but the mail:fwdAddress will be empty. Example:

mail:userID = " mailuser1"

mail:userGUID = "A961DAFE-2FE5-4EEC-A2CB-CB6511E9B28D"

mail:fwdAddress = ""



If an incorrect ID was used or does not exist, the following message will be returned:

mail:error = "user not found"
To see which accounts currently are being auto-forwarded
Execute this command:

sudo serveradmin command mail:command = getAutoForward
The command returns a list of user GUIDs and the auto-forward addresses. For Example:

$ sudo serveradmin command mail:command = getAutoForward

mail:1080C8CF-5432-4302-B3B7-0EEFB79106AD:fwdAddress = "my-userID-1@example.net"

mail:2DD1FB33-340F-408F-8C2A-D77B0A2431C7:fwdAddress = "my-userID-2@example.net"
Learn more
As an alternative, you can also use the set_user_mail_opts command. See man set_user_mail_opts for usage and options.