Route mail to a mail enabled contact

I want to create mail enabled contacts for 500 mailboxes in a company were aquring and do away with their mailboxes.  Then create mailboxes here at my domain but any mail sent to their old company email have that domain route the mail using the mail enabled contact so I would create the contacts add the external address as "newcompanydomainEmail".  Then  add a smtp address to the contact for the "existing domain email".  Correct?

Im using this script to create the contacts with an CSV that gathered names and mail address .

 Import-Csv “contacts.csv” | ForEach {New-MailContact -Name $_.Name -Firstname $_.FirstName -LastName $_.LastName -ExternalEmailAddress $_.ExternalEmailAddress -OrganizationalUnit “Domainname/OUname”}

How can I add the smtp address using a script and where do I make a rule or whatever to have the mail rout through this contact so I can delete their mailboxes on the olddomain?
Twhite0909Asked:
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Delphineous SilverwingGood Ol' GeekCommented:
If I have interpreted your goal correctly, you only need to create a mail contact with their old smtp address and the external address as their new address on your system.

SMTP address=johndoe@oldcompany.com
EXTERNAL address=johndoe@newcompany.com

That's it. No routing necessary as long as the old servers are online. When the old Exchange server receives the e-mail for johndoe@oldcompany.com, it will recognize that address as belonging to an external contact and automatically send the message to johndoe@newcompany.com.

Ideally, their new mailboxes at the new company will have the old company address with the MX records for the domain pointing to the new company. Then the contacts and old company servers wouldn't be necessary.

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Jian An LimSolutions ArchitectCommented:
i think is more to convert them to mail-enabled user. or use of targetaddress will be better solutions then create 500 contacts.
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