From: Philippe Verdy (email@example.com)
Date: Thu Jan 04 2007 - 15:56:58 CST
From: "Rick McGowan" <firstname.lastname@example.org>
> Philippe is correct:
>> once a message is sent, it generally can't be canceled, because
>> email forwarding is really too fast
> Messages are queued on the server within seconds, and by the time 3
> minutes have elapsed, most of the queue has already been delivered
> off-site. The only way to get rid of whatever stragglers are in the queue
> is to call me on the phone within seconds of sending your message, and
> having me shut down sendmail and flush immediately. Usually, this is a
> losing proposition because no matter how fast we are, hundreds of copies of
> the message have already been delivered.
> However, on the positive side, seriously mistaken messages (confidential
> info, viruses, hate-mail, etc) can be removed from the archives when
But is there a way to manage the delay before the delivery to all subscribers, by sending:
* first immediately back to the sender (if it can be checked by verifying its connecting SMTP which should be part of allowed IP ranges for each subscriber, and checked), so that it can cancel immediately
* possibly immediately to a fewauthorized users with privileges that can cancel intrusive messages
* then after some reasonnable delay (15 minutes?) to other subscribers
This would be a setting of the listmanager itself, not directly of sendmail which is invoked by the MLM and starts sending immediately as soon as he can. Ithink that the MLM alreadycontains settings to filter known spams, too voluminous emails, and already performs a checkfor allowed senders (however I don't know how he checks senders: does it trust "From:" in the headers or FROM in the enveloppe, or the HELO string (all these are easily forged by spammers)?
The only verifiable and trustable(?) info is the IP of the incoming SMTP sender, or the presence of secret authorization keys in the email, that the MLM would check and remove before forwarding messages to others.
The problem with the IP is that most regular subscriber don't know exactly the IP of the SMTP server that is forwaring their email to the list, because it is managed by their ISP, and this ISP may have tons of distinct SMTP servers for outgoing emails (and even these IP change regularly without notice).
However, regular subscribers using the STMP server of their ISP will be seen as sending emails from an IP that reverse-resolves to a host in the domain of their ISP; this is a minimal check, but if only one domain is allowed, the domain of the email address of the sender, it will be inconvenient if that subscriber is currently connected to the Internet using another ISP, requiring them to use outgoing SMTP servers from this other ISP (or using wellknown external webmails like YahooMail, GMail, MSN, and so on which may be trustable if they have their own antispam filters for their outgoing emails).
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