PowerShell: assign send-as permissions to Exchange 2003 mailbox
On Exchange 2007 this is easy, but what if you have PowerShell without the Exchange 2007 provider? See below to assign send-as to a mailbox on regular PowerShell for Exchange 2003. The GUID as used in the script is an ExtendedRight which is listed on the Microsoft site (http://www.microsoft.com/technet/scriptcenter/topics/security/allrights.mspx).
$AccountName = "DOMAINusername"
$acl = new-object System.DirectoryServices.ActiveDirectoryAccessRule ([Security.Principal.NTAccount]$AccountName, 'ExtendedRight', 'Allow', 'ab721a54-1e2f-11d0-9819-00aa0040529b')
$Mailbox.get_ObjectSecurity().AddAccessRule($acl)
$mailbox.CommitChanges()