Dear, I have one user that cann't send e-mail from pop3 with the following error Task 'email@domain.com - Sending' reported error (0x800CCC78) : 'Cannot send the message. Verify the e-mail address in your account properties. The server responded: 550 5.7.1 Client does not have permissions to send as this sender' when I check the user security I found out that the checkbox for (send AS) for user SELF is not checked I return it back then after one or two days it is unchecked again I have removed the user and then create a new one with the same properties and connect the mailbox to the new user , the again it worked for one day and this checkbox again unchecked please help to solve this issue Regards,

Dears, any help about this issue. Regards.

Please describe the exchange topology, and client Does the same issue happen to other clients with the same configuration? Please run the ExBPA against the exchange server for permission checkJames Luo TechNet Subscriber Support (http://technet.microsoft.com/en-us/subscriptions/ms788697.aspx) If you have any feedback on our support, please contact tngfb@microsoft.com

thanks for replying it has been solved by remove the user from server operator group by following this link http://support.microsoft.com/kb/912918 Regards,