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Re: looping problem

2002-02-25 10:28:55
At 11:28 2002-02-25 -0500, peter(_at_)compclass(_dot_)com wrote:
I sent an email to the list over the weekend but I got no copy in my own
mail box so I don't think it got out. If this is a repeat, I apologize,
but I haven't seen any responses either, hence the resubmit.

FTR, weekends are typically slow for a lot of lists, since some people endeavour to have lives. However, I didn't see your post anyway, so either it got munched up by my spam filters, or it didn't get to the list.

Hmm, perhaps you didn't see it because it was refused because the listserv didn't reply with the phrase that pays?

I have a spam filter (right out of Stopping Spam - O'reilly) that bounces
mail back to the sender if they aren't recognized and/or authorized via a
key phrase.

Hopefully, you've pre-filtered this list, because I'm not about to jump through hoops so that you can accept an answer to your own question. I doubt I am alone in this thinking.

My problem is, what to do if both sender and receiver have
this filter?

That's really difficult to say without seeing the filter - and while I have a large library of ORA books, I don't own that particular one, so I cannot refer to it to see what you're talking about.

I'm thinking that I can add a string to the subject line on
the outgoing bounce or scan the entire message body for my original bounce
message. The latter seems safer but more CPU intensive.

Try adding an "X-Loop:" header (somewhere down in where you create the bounce message - probably in the same invocation which _likely_ used formail to generate an auto-reply header). The basic syntax would be like:

:0f
| formail -A "X-Loop: myaddress"

(the above assumes that it'd be placed within a braced construct which is only executed when your autoreply is being triggered).

At the outter layer of your whole bounceback system, you'd add an INVERTED check for this X-Loop:

* ! ^X-Loop: myaddress

(i.e. execute the bounceback ONLY if there isn't an X-Loop header).

If the authors of the book in question didn't put such checking in their filter to begin with, I'd closely examine anything else you got from the book, because X-Loop checking is the most basic loop prevention method there is. It isn't infalible (if the filter you're using doesn't reply with the headers retained and instead generates a fresh message, then the header will be lost on the reply), and of course you should actually TEST it, either using two accounts, or by manually piping a test message into the filter (see the sandbox described in my disclaimer). Without seeing the filter, it's a bit difficult to point WHERE to stuff some tweak.

---
 Sean B. Straw / Professional Software Engineering

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