Error after 'Send on behalf' or 'Send As'

After configuring a 'send as' or 'send on behalf of' user may receive this message:
"You are not allowed to send this message because you are trying to send on behalf of another user without permission to do so. Please verify that you are sending on behalf of the correct sender, or ask your system administrator to help you get the required permission." or "You do not have permission to send on behalf of the specified user."

You must check the following:

1- Ensure that you have configured correctly the 'send as' or the 'send on behalf of'
     -To configure the 'send as' by Poweshell
      Add-ADPermission "John Simpson" -User "Domain\User" -Extendedrights "Send As"
     -To configure the 'send on behalf of' by Powershell
      Set-Mailbox UserMailbox -GrantSendOn BehalfTo UserWhoSend

2- Ensure that the mailbox is not Hidden from address lists
     - Open the EMC
     - Open the concerned Mailbox
     - uncheck the option 'Hide from Exchange address lists'

Announcing Exchange 2010 Service Pack 2

The Exchange Team announced the Exchange 2010 Service Pack 2.

http://blogs.technet.com/b/exchange/archive/2011/05/17/announcing-exchange-2010-service-pack-2.aspx

Hub Transport installation failed with "An unexpected error occurred while modifying the forms authentication settings for path /LM/W3SVC/1. The error returned was 5506."

To solv this issue Try the following:
1- Open IIS administration console
2- Right click "Default Web Site"
3- Click "Edit Bindings..."
4- Remove all bindings refering to port 443
5- Reinstall
Good Luck