We're having problems with one of our servers. We have a mailbox that is set up for the purpose of several users having access to it and being able to send from it. To achieve this I have just right clicked on the mailbox and selected manage send as permissions. From here I've added the users. Something that has worked for me on many Exchange 2007 servers in the past.
however, this time the permissions disappear without any reason I can isolate. Something that seem to happen every hour or so. When I go back to check the send as permission box is completely empty.