Hi , We are using the Exchange 2000, I have give the proper mailbox rights to the users to access the mailbox for that users , even thaugh when user is sending the mails from that mailbox , the mail which he is sending is getting the bounce , with the error report says that you do no having the proper permission ...how can i resolve it ...Please Help ....John

Microsoft cannot make up their mind on how they want to handle "send as" in Exchange. Sometimes its part of "full mailbox" rights and sometimes its seperate. They've changed it back and fourth a few times with different versions and service packs. for exchange 2000 and 5.5 its pretty simple: http://support.microsoft.com/kb/281208 Exchange 2000 To grant a user send as rights to another user's mailbox in Exchange 2000: 1. Start Active Directory Users and Computers; click Start, point to Programs, point to Administrative Tools, and then click Active Directory Users and Computers. 2. On the View menu, make sure that Advanced Features is selected. 3. Double-click the user that you want to grant send as rights for, and then click the Security tab. 4. Click Add, click the user that you want to give send as rights to, and then check send as under allow in the Permissions area. 5. Remove all other permissions that are granted by default so that only the send as permission is granted. 6. Click OK to close the dialog box. for 2003 read: http://support.microsoft.com/kb/895949 for 2007 read: http://msexchangeteam.com/archive/2006/09/05/428833.aspx