How to: Send As permissions and how long it takes for them to apply

Most of you are familiar with the send as permissions that you can assign to a User in order for him to be able to send messages as another User.

The process of doing that has been simplified in Exchange 2007. In Exchange 2003 you will have to use Permissions on the user object in order to do that, in Exchange 2007 is just one click away J

Just open Exchange Management Console and locate the user that you wish to assign the send as permission.
In our example we wish UserA to have permissions to send messages as UserB, so we locate UserB and select "Manage Send as Permissions"

Then we have the option to select the user that will be able to send as UserB, so we select UserA.
Click Add on the Manage Send As Permision Wizard and select the appropriate User

 

 Click Manage and you are done! :-)

 Well the issue that we faced here is that when you assign send as permissions to a user they are not enforced immediatly.

After some research this is a normal behavior and is due to the Information Store Cache that by default refreshes Mailbox Settings every 120 minutes
from Active Directory. So when assigning Send as permissions you will have to consider Active Directory Replication Latency between the Domain Controller that
the mailbox Server is using and the one you made the changes and add the 120 minutes that Information Store refreshes information about Mailbox Settings.

You can oufcourse tweak this setting but be carefull when doing so, you add load to your Domain Controllers, Mailbox Servers and Network.
You can find more information about the Mailbox Cache in this link : https://technet.microsoft.com/en-us/library/aa998523.aspx
Note: Mailbox Cache also applies to Mailbox Quotas, so don't expect them to take effect immediatly after you configure them.