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Re: Latest proposal re HELO checking: make HELO tests optional

2004-03-11 06:56:33
On Thu, 2004-03-11 at 07:14 -0600, wayne wrote:
Are you saying that you these conditions never happen?  If it happens,
it is not just 'the potential', if not, you could just drop drop the
bounces so that there isn't 'the potential'.

I cannot do that. It would make my system unreliable, and my users would
rightly object. We cannot throw the baby out with the bathwater.

The status quo for years was for everyone to be an open relay also.  
For the last few years, there has been a similar change to reject
email during the SMTP session rather than acccepting email and then
generating a bounce.

As I said, I do that as much as possible. The _only_ circumstance in
which my machines will accept unauthenticated mail which they _may_ have
to bounce is if they are performing MX backup services for a domain and
the primary MX host is actually unreachable. If that happens, then a
bounce may be generated _iff_ the destination address is invalid. No
other circumstances will cause a bounce. 

 As far as evidence, you can view the IETF
BOF video and see an AOL person who says that they do this, and I have
a private email from MicroSoft people who directly say that large
quanities of email is thrown on the floor by Hotmail/MSN.  (This is
only done if the email has a "high probability" of being spam.)

I prefer to reject such mail at SMTP time instead of only making the
decision afterwards. I also insist that domains for which I provide MX
services do not reject mail from my machines based on content checking.
Either they're satisfied with the content checking I do on their behalf,
or they ask me to be stricter; causing bounces by rejecting mail offered
by the MX backup is not acceptable.

If you think bounces are so bad, why don't you start rejecting all MAIL
FROM:<> ?

Bounces are good.  Bounces to innocient third parties is bad.

Bounces to innocent third parties are less of a problem than a _lack_ of
bounces to genuine mail which has gone astray.

I could refuse to provide MX backup services for any domain for which I
don't have a current (and constantly updated) list of users, in order to
avoid the rare circumstance in which my machines could generate a
bounce. But I choose not to do that. The pain of keeping the user lists
up to date would be too high, as would the pain of not having a backup
MX and being able to flush the queue with ETRN after an outage. YMMV.

-- 
dwmw2


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