Well, I answered my own question on making sendmail bounce messages back to
/usr/lib/sendmail -t -oi -oem
/usr/lib/sendmail -t -oi -oem -ba
But sendmail then replies to the From: header instead of the Errors-To:
header. Oh well.
Doesn't look like something I'd want, but it seems to work in this case...
-ba Go into ARPANET mode. All input lines must
end with a RETURN-LINEFEED, and all messages
will be generated with a RETURN-LINEFEED at
the end. Also, the From: and Sender:
fields are examined for the name of the