Subject: Annoying stupid non-conforming auto-responders! (was: Re: SPAM -> Re: [hackers-il] My "Stop Using (and Teaching) C-Shell and Tcsh" Page)

From: "Arik Baratz" <[email-masked]>
Date: Sun, 7 Oct 2007 04:44:04 -0700

On 7 Oct 2007 11:06:51 -0000, [email-masked]  <[email-masked]> wrote:
> Hi,
>
> My e-mail has been changed.
> Please, re-send your e-mail to my new e-mail address which
> can be found at  http://www.breakt.co.il/~alexr/alex_very_secret_email.html
>
> Thank you!
>
> Alex
>

<rant>
I tell you, if I had a web site with a folder named "anti", I would
write a piece about these auto-responders there.

People, there is an RFC, and it's number is 2821. Please please
please, before you write any piece of software that deals with email,
be it an MUA, MTA or any piece of code, ESPECIALLY if said piece of
code runs unattended, DOUBLY SO if said piece of code responds to an
email message automatically. If you don't feel like reading the RFC,
don't write the code.

Unfortunately, if you do decide to not write the code and use an
existing piece of code, you're still not guaranteed that the code is
compliant. Actually it is un-compliant, more likely than not. The sad
state of affairs is that indeed people don't write good compliant code
when it comes to auto-responders, and there's more crap out there than
anything else. Perhaps because writing an auto-responder or a vacation
program is a task that looks insignificant. I don't really know.

The two golden rules about auto-responders, which unfortunately most
do not comply with are as follows:

1. If you are an automatic piece of code replying to email, you MUST
reply to the envelope address (and if you're not an MTA, to the
address in the "Return-Path" header, which is where the MTA should
have put the envelope address). It's a MUST. If there is no envelope
address, do refrain from sending the message.

All (well written) lists put their bounce address there, which will,
in short order, unsubscribe the user from the list due to excessive
bounces. Other lists put the list owner there, which is the person
responsible for bounces. What you should absolutely MUST NOT do is use
the "From" or the "Reply-To" headers. They're only meant for MUAs. You
have no business looking there.

2. If you generate an automatic reply, you MUST leave the envelope
address empty. This is an equally important rule, because together
with rule 1 it will stop mail-loops from being formed. An empty
envelope address is perfectly legal and conforming to the
aforementioned RFC.

Quoting from [1]:
   If there is a delivery failure after acceptance of a message, the
   receiver-SMTP MUST formulate and mail a notification message.  This
   notification MUST be sent using a null ("<>") reverse path in the
   envelope.  The recipient of this notification MUST be the address
   from the envelope return path (or the Return-Path: line).  However,
   if this address is null ("<>"), the receiver-SMTP MUST NOT send a
   notification.

Alex's auto-responder fails on both counts, which makes me want to
send him a message with himself in the "From" header about 100 times,
just to see his hosting and traffic costs go up as his auto-responder
goes into a loop. But I wouldn't do it. I'm not that bad.

I'd like to mention one particular widespread non-compliant program,
Microsoft Outlook's Out Of Office Assistant (which actually executes
inside Microsoft Exchange). Yes, it's non-compliant. It half-redeems
itself by saving a cache of the addresses it responded to and refrains
from sending messages to them again. Let's see if Alex's
auto-responder does that, I'll know as soon as I'll send this
message...
</rant>

Take care, do good.

-- Arik

[1] RFC 2821 section 6.1

---

From: "Nadav Har'El" <[email-masked]>
Date: Sun, 7 Oct 2007 14:39:42 +0200

> write a piece about these auto-responders there.

My two favorite out-of-office messages are this:

   "You are receiving this automatic notification because I am out of the
    office. If I was in, chances are you wouldn't have received anything
    at all."

   "I will be unable to delete all the unread, worthless emails you send me
    until I return from vacation. Please be patient and your mail will be
    deleted in the order it was received."

:-)

-- 
Nadav Har'El                        |      Sunday, Oct  7 2007, 25 Tishri 5768
[email-masked]             |-----------------------------------------
Phone +972-523-790466, ICQ 13349191 |Cats aren't clean, they're just covered
http://nadav.harel.org.il           |with cat spit.

---

From: Omer Zak <[email-masked]>
Date: Sun, 07 Oct 2007 14:07:27 +0200

Arik's rant deserves a Nobel prize.

Arik described the problem, where to find the solution, and even
(briefly) the solution itself.

I am honored to save the rant in my archival folders, for future
reference.
                                 --- Omer

> <rant>
[... snipped ...]
> People, there is an RFC, and it's number is 2821.
[... snipped ...]

-- 
One does not make peace with enemies.  One makes peace with former
enemies.
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