On Tue, 9 Dec 1997, John Gianni wrote:
Q: Are there known problems with "valid" mails with illegal MessageIDs?
Yes. (see below)
The reason I ask is that our most successful anti-spam filters to date are:
Bad-Message-ID's (era eriksson, procmail-d Digest V97 #308, et. al.)
Ban-Repeat-Spam (very many contributors over time)
But, the bad-message-id filter catches few (very very few) emails from
valid users (who apparently, for some strange reason, are sending out email
with bad message id's). That wouldn't be much of a problem, except that
our MITS department won't even consider fixing the bad-message-id unless
it causes a problem somewhere else.
Why would they not consider fixing it? Their e-mail software/gateway is
broken, and needs fixing. That's that. Direct them to RFC 822, sec 4.6.1.
<URL:http://ds.internic.net/rfc/rfc822.txt>.
I ask:
a) Are there any real problems with a user sending mail, unknowningly
containing a bad message id?
Yes. Some of the problems are:
Some people (myself included) run filters to automatically delete
incoming e-mail if its message-ID has been seen recently, or if
it looks bogus.
Some mailing list software (including Smartlist) does not accept
e-mail with a message-ID that has been seen recently. Each message
must have a unique message-ID. The best way to ensure that msgids
are unique in a global context is to include a fully-qualified
domain name after the '@'. In particular, a message-ID like
<3(_dot_)0(_dot_)5(_dot_)32(_dot_)19971208192547(_dot_)007db100(_at_)mailhub >
is unacceptable for
this reason (even if it didn't have a space at the end.)
Some mail archive software (including some that I wrote) uses
message-IDs as a unique identifier for that message in the archive.
It may reject messages that appear to be duplicates because they
have a message-ID used by other messages. (as my software does.)
b) How can this occur in the first place -- how could our user accidentally
send out email with a bad message id?
Their software or gateway is broken. They should consult a local
system administrator to get it fixed.
Hope this helps,
Gerald
p.s. One day I want to set up procmail filters to send autoreplies
to people using broken software, explaining what's wrong and
how to fix it.
:
And, here is both the response from our MITS department, & the problem header:
From: "Omar Keblawi -MITS" <keblawi>
To: alexand, John Gianni <jjg>
Subject: Re: Bad message id -- do you know why?
John or Jennifer,
What kind of problems is this causing for you?
Omar
On Dec 9, 10:53am, John Gianni wrote:
Subject: Bad message id -- do you know why?
Do you know what is wrong with Jennifer's message id?
It might be the space at the very end, before the closing angle bracket.
Or, something in between.
Message-Id:
<3(_dot_)0(_dot_)5(_dot_)32(_dot_)19971208192547(_dot_)007db100(_at_)mailhub
>
: