hi

i wish to restrict email sending / receiving for a specific domain or email id ie for example it my customer company has a policy that the certain users cannot send any emails other that their client domains or there may be a company wide policy that no email user can sent or receive emails from gmail.com or hotmail.com or yahoo.com.

how do it set such restrictions in postfix at an smtp level.

further on are there any means to handle data leak prevention such as credit card numbers and other sensitive data

thanks and regds
rajesh