postfix different behavior for mail command and python smtplib

[Mayuresh <mayuresh%acm.org@localhost>]

I have some `protected destinations' settings on a postfix server on
NetBSD8. Skipping the details as those are irrelevant.

When I use mail command as a local user on the same machine postfix is
accepting and delivering emails to the protected destinations, though
those senders are not a part of senders list allowed to send to the
protected destinations.

However in a web app I am trying to use smtplib.SMTP in pyonth3 to use the
same from address and same protected destination. This time postfix is
seen blocking the mail as it is not from the permissible senders' list.

I actually desire the behavior where local user on the machine would be
allowed to send to a protected destination - just like postfix is allowing
it for the mail command.

Is there a way to find the exact difference between mail command's
behavior vs smtplib and achieve the desired behavior?

-- 
Mayuresh