How to Block sending mails via telent in postfix
 

Hi,

I implemented postfix as mail gateway but i need to block the ability to send
mails via telnet

How can i achive this????Please help me

You can't, the mta has no way of knowing what is being used to send the email ie telnet .in this case.

Reject mails on Postfix via telnet session
 

I think you can develop a cleanup filter (header_checks for example) that checks if the message-id contains @myhostname.mydomain .
This hasn't been tested and also it will reject some of the NDRs.