Kamal Paryani wrote:

can we have a restriction on any linux based mta

"any linux based mta" is a very broad term.. tell us what mta are *you* comfortable with.

namely

a particular user is allowed to send email to only list of authorized mail address - say a list of 20 people , he should not be allowed to send mail to anybody besides the people on this list

it is possible in postfix (using restriction_classes) and qmail (using .qmail perl/shell scripting), i do not work with sendmail/exim etc and can't comment..