You have created a user lets say Charlie Brown/MyCompany and you say that the user has been created correctly. Then you try to open the mail DB for the user and get an access denied. Are you logged in as Charlie Brown/MyCompany or are you logged in as Satish Reddy/MyCompany? If you are logged in as yourself then the ACL of the new Mail DB probably does not contain your name. If you are logged in as Charlie then the ACL is probably corrupted. as suggested above.