OT? /dev/null 5.1.1 email

[Jim Popovitch <jimpop () yahoo com>]

<disclaimer>
I know this is an email-only question, however the value of the feedback
from NANOG is greater than elsewhere, imho.
</disclaimer>

Should undeliverable email (5.1.1, User unknown) be directed
to /dev/null rather than responded to?

I was always under the impression that it was nice to respond with a
polite message, however these days it seems that 95% of the polite
responses are going to 5.1.1 addresses themselves.

Tia,

-Jim P.