Multiple SendOnBehalfTo in EMS

If you use the Exchange Management Shell to define the SendOnBehalfTo property of an Exchange 2010 mailbox then the user that you provide overwrites any existing users with SendOnBehalfTo permission. This happens because the list of users is stored as an array. When you provide a single user, you overwrite that list with the single user. Instead, you need to add a user.

This is not the most concise way to do it. I just find it understandable this way.

#Get current list of users
$mailbox=get-mailbox "HelpDesk"
$SendList=$mailbox.GrantSendOnBehalfTo

#Add to list of users
$newperson=get-user "NewPerson"
$SendList=$SendList + $newperson

#Set new list
Set-Mailbox "HelpDesk" -GrantSendonBehalfTo $SendList

For more details about why this works see my posting on adding additional managers to a distribution group at http://byronwright.blogspot.com/2011/08/adding-additional-distribution-group.html. It uses a similar process to modify the list of managers