The mailing list for listmasters using Sympa

[Jose-Marcio Martins da Cruz <address@concealed>]

Hi you and all,

Nick Holden wrote:
> Hi all,
>
> Is anyone else noticing problems with the use of "listname-subscribe"
> and "listname-unsubscribe"?
>
> Specifically, it appears that at least one major ISP (virgin, which took
> over ntl in the UK last year) is now refusing to transport entirely
> blank email messages. As a result blank email messages to
> listname-subscribe or listname-unsubscribe do not get through to my
> server from users on those networks (including me, which is how I
> noticed it).

...

> But first, have other list managers noticed the same problem?

I don't know about other people seeing the problem, but I know why they 
do that.

We're a domain with some, say, 2000 users. I usually see here something 
like 10 to 50 empty messages a day. Some of them are very short and have 
only a short code in the body (10 chars or even less).

This kind of message is used by, very probably, spammers to check the 
validity of an email addresses. Suppose they have a database of some, 
say million email addresses and want to check if their are still good. 
So they send this kind of probes. They don't need to send the probes in 
a high speed. They do that in a continous way, with a reasonable speed, 
like 20000 a day (against 50000 thousand spams an hour).

The problem is that if your mailserver accepts the message, the spammer 
will interpret that as : "the probed address is a valid one !!! If you 
reject, that means that the recipient probably doesn't exist. It's 
better to reject...

I've checked some of the supposed sender addresses I've seen. All of 
them are valid addresses and, probably, controlled by the spammer in 
order to collect all bounces and process them to maintain their 
addresses database.

As long as the message is very very short, no content filter can, 
detect, in a reliable enough way, it it's a spam or a legitimate message.

In France (and in some other countries probably too), collecting or 
maintaining a database of email addresses is illegal. So accepting this 
kind of messages is a privacy issue.

The false positives I've seem are, as you said, messages to MLM and some 
notifications from Gmail Calendar and Agenda - if you don't have any 
event schedule for the day, gmail will send you an empty message.

One possible solution is to allways have a signature in your message... 
But I agree, this isn't a good solution.

Well, that's the problem...

My 2 cents

José-Marcio

> Thanks
>
> Nick


--
 ---------------------------------------------------------------
 Jose Marcio MARTINS DA CRUZ           http://j-chkmail.ensmp.fr
 Ecole des Mines de Paris
 60, bd Saint Michel                      75272 - PARIS CEDEX 06
 mailto:address@concealed