Sendmail dying?

[David Kanter <david.kanter@mindspring.com>]

Sendmail sometimes will, sometimes won't re-write the From: header. Is this
bizarre?

When it re-writes the header (whether I use Mutt or mail) everything is
great. But when it doesn't re-write the header the mail gets rejected
because it's from an unknown host (450 error, as it should since I've called
my home machine "openbsd.mindspring.com"

But I don't understand why it will re-write the headers only some times but
not others.

Can anyone think of an explanation for this?
-- 
David Kanter