from "Kaushik  N" <nkaushik77@rediffmail.com>:

> I would like to block all emails from any user to a particular address. How do i do that in NetBSD?
>Also how do I send binary files as attachment in email from the command line?

Somebody has already answered your first question, better than I could, but on
the second, I noticed an mpack in the packages collection (pkgsrc) whose
description matches the mpack I use in DOS, mainly to extract attachments, 
though I once used it to send an attachment somebody requested from me.  
There is a command to attach (mpack) or extract (munpack), and then you would
use your preferred command-line SMTP program to send it.  mpack is something
good to have on hand, and not bloated.