correct behavior for MTA error message?

[Omar Thameen <omar @ clifford . inch . com>]

Hi,

I've run into a minor loop problem where an MTA couldn't deliver a
message, and reported this fact to the address in the "reply-to" field
of the list, which was set to the list itself (yes, I warned them of
such danger).  I assume that sending undeliverable-type messages to the
reply-to address is not RFC compliant.  Does anyone know offhand
what address it's _supposed_ to send errors to and what RFC specifies
this?  I checked 821 and 822 and didn't see anything specifically
addressing this behavior.

Is the preferred method of dealing with this to insert a header into
all outgoing messages like
X-Loop-Avoid: whatever
and then add it to taboo_header and taboo_body (taboo_body since
the offending MTA will probably quote the message with headers).

Thanks,
Omar