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WWW Virtual Library

Aggressive email filtering

The WWW VL home page

SPAM is a nuisance (to put it mildly).

There are certain sources of email that one might logically choose to block (such as 'open relays').

However, various people/organisations have taken it upon themselves to draw up far wider lists of sources. Some of these lists are even reported to run to permanent IP numbers assigned to business ADSL lines (just because they are ADSL). Some systems reject messages if the source IP does not match a reverse DNS look-up (fraught both because the sending mail server may not be same as the recipient server if one runs several servers, and because reverse DNS (as anyone who looks at weblogs knows) is not always 'easy').

The main 'quick fix' is though to block all mail from dial up, or other dynamic, connections. Thus cutting mail from normal modem, ADSL modem, external Wifi/WLAN, etc. users.

Having spoken to those insulated (or ?isolated) by such techniques, one hears they are still deluged in spam. So any 'success' is obviously relative.

In effect this is akin to trying to stop unwanted telephone calls by blocking all calls from telephone boxes / telephone kiosks. (It also seems as futile as 'the lists' do not seem to block all dynamic addresses.)

Yes, one could send all one's email via a fixed server. Just as one could call head office from a telephone kiosk and ask them to patch you through to a paranoid telephone user. If (see above), it would solve the problem it might be worth considering. Some would certainly see it as a 'security' advantage that all emails had to go through a fixed outgoing server …

Surprisingly, the main (in effect anonymous) email account providers (e.g. gmail.com) do not seem to use these techniques, nor to suffer these problems. Those who want to communicate (major international businesses, international law firms) also do not seem to use these techniques. The worst cases seem to be academic establishments in a few countries and some small ISPs that 'protect' their customers.

Lately the problem has been compounded as seemingly some of the implementers of these policies, which are at least arguable, have started to 'silently fail' email that they do not like. If your ISP is so discourteous as to delete email addressed to you without telling you and without telling the sender … are you surprised when you do not get replies?

The WWWVL is run by volunteers. By necessity they will respond to emails, where they are and how they can. If you wish to communicate with such a group please use an email account that accepts emails! Thank you.


There are, BTW, much better ways of dealing with unsolicited emails, just as with dealing with unsolicited phone calls. But, that is another matter altogether.


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