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From:  "L-Soft list server at Humber College (1.8c)"
Date:  Fri Jan 25, 2002  11:00 am
Subject:  Subscription probe for SW-L - please ignore

Fri, 25 Jan 2002 06:00:01

This message is a "probe" for your subscription to the SW-L list. You do
not need to take any action to remain subscribed to the list, and in
particular you should not reply to this message. Simply discard it now,
or read on if you would like to know more about how this probing
mechanism works.

A "probe" is a message like the one you are reading, sent to an
individual subscriber and tagged with a special signature to uniquely
identify this particular subscriber (you can probably not see the
signature because it is in the mail headers). If the subscriber's e-mail
address is no longer valid, the message will be returned to LISTSERV and
the faulty address will be removed from the list. If the subscriber's
address is still valid, the message will not bounce and the user will not
be deleted.

The main advantage of this technique is that it can be fully automated;
the list owner does not need to read a single delivery error. For a large
or active list, the manpower savings can be tremendous. In fact, some
lists are so large that it is virtually impossible to process delivery
errors manually. Another advantage is that the special, unique signatures
make it possible to accurately process delivery errors that are otherwise
unintelligible, even to an experienced technical person.

The drawback, however, is that this method lacks flexibility and
forgiveness. Since the Internet does not provide a reliable mechanism for
probing an e-mail address without actually delivering a message to the
human recipient, the subscribers need to be inconvenienced with yet
another "junk message". And, unlike a human list owner, LISTSERV follows
a number of simple rules in determining when and whether to terminate a
subscription. In particular, a common problem with automatic probes is
mail gateways that return a delivery error, but do deliver the message
anyway. LISTSERV has no way to know that the message was in fact
delivered, and in most cases the subscriber is not aware of the existence
of these "false" error reports. If this happens to you, LISTSERV will
send you another message with a copy of the delivery error returned by
your mail system, so that you can show it to your technical people.

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