Before CU2 you could only send email in exchange 2013 to an external contact via power shell, Now we can do it via the EAC also. Below we do it via the EAC first, scroll down to see how to forward to a contact in Exchange 2013 powershell.
Send Email To External Contact Via GUI / ECP
To start open the EAC and create a new Mail Contact in Exchange 2013 with the correct name and External SMTP email address.
Recipients > Contacts
Once done browse to the mailbox that you would like to forward mail from to the new contact and choose edit, then select Mailbox Features and Mail Flow.
Recipient > Mailboxes > mailbox > Mailbox Features > Mail Flow
Then simply enable Mail Forwarding , browse and select the Mail Contact we created in the earlier step.
Its quicker in power shell though. Below you will see commands on how to forward email in exchange to external contacts 2013 in power shell.
Exchange 2013 Powershell – Forward To External Contact
First the command, then the description.
Set-Mailbox -Identity "Allen" -DeliverToMailboxAndForward $true -ForwardingSMTPAddress firstname.lastname@example.org
The command above will forward all emails from the mailbox “Allen” to Allen@hotmail.com and also leave a copy of the email in the Allen mailbox in Exchange 2013
Set-Mailbox -Identity “Allen” -DeliverToMailboxandforward $False -ForwardingSMTPAddress $Null -ForwardingAddress $Null
The command above will STOP the forward of all emails from the mailbox “Allen” to Allen@hotmail.com due to the $false command.
Remember, after the -deliver use the “TAB” button to see all forwarding options.