[lug] A .forward standoff

Hugh Brown hugh at math.byu.edu
Tue Jun 14 15:57:14 MDT 2005

I mispoke slightly.  The message would die after hitting a maximal hop
count.  However you could cause all sorts of messes and manual
intervention may be required to stop the loop.

e.g. in sendmail you could do

user: \user

in the aliases file that would cause the ~user/.forward file to be ignored
until the offending .forward file were fixed.

I asked a colleague and he said that they had a user once with accounts on
three separate servers and would forward mail on each server to the other

e.g. A would forward to B and C; B would forward to A and C; C would
forward to A and B

so it would fork and loop.  The user got his mail account disabled. :)


On Tue, 14 Jun 2005, Matt Thompson wrote:

> OK, I'm kind of ashamed that I didn't know the answer to a question a
> friend posed me.  It seems like something I should know, but I never
> thought about it.  I also couldn't find the answer on Google, but that's
> probably due to noise on my searches.
> Namely, say you have two mailservers, A and B. In A, you have a .forward
> pointing to B, and in B a .forward to A.  What occurs when you send mail
> to one?
> I'm sure this situation has some ARPANET-era jargon/USENET name that I
> don't know, and there is probably a paragraph about it in the Sendmail
> doorstop that I overlooked.  Heck, maybe one of you even tried it once
> to see.
> Wondering away,
> Matt
> --
> The mayfly lives only one day, and sometimes it rains. - Geo. Carlin
>    Matt Thompson -- http://ucsub.colorado.edu/~thompsma/
>    440 UCB, Boulder, CO  80309-0440
>    JILA A510, 303-492-4662

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