I recently had to add an additional SMTP Address for all the users in my domain. I wrote this quick script that made it a no brainer:
This script adds a new smtp address of email@example.com
to all email users that have an @yourdomain.com email address
1.0 - 12/21/2011 Initial release
None. You cannot pipe objects to this script.
$mailboxes = Get-Mailbox -resultsize unlimited -RecipientTypeDetails UserMailbox"
foreach ($mailbox in $mailboxes)
$newaddress = $mailbox.windowsemailaddress -replace '@yourdomain.com' , '@exchange.yourdomain.com'
$mailbox.EmailAddresses += $newaddress
Set-Mailbox -Identity $mailbox.alias -EmailAddresses $mailbox.EmailAddresses