So here is what I am trying to do:

As part of user creation I have it creating an onsite mailbox with exchange, but I need to create another mailbox for that user for our Avaya phone system. For example:

User: Rob Hawker

username: rhawker

I create a mailbox for rhawker, but I also need to create a mailbox for "VMRhawker" This is a separate mailbox from the rhawker one. I am trying to accomplish this by running a customer script. :

Add-PSSnapin Microsoft.Exchange.Management.PowerShell.E2010;

$user = %username%

$displayname = %displayName%

$pw = %password%

$db = 5

new-mailbox -name VM$user -password $pw -database hqdb0$db -alias VM$user -displayname "$displayname" -organizationalunit corp.<domain>.com/Exchange/VoiceMailOnly -userprincipalname VM$user@domain.com

start-sleep -s 10

set-mailbox -identity VM$user -hiddenfromaddresslistsenabled $true 

this script works when run manually and when I run it in the user creation task it says that it is running in the background, but nothing happens. IT does not create the mailbox. 

Can someone point me in the right direction?

-Rob