February 09, 2004
''Greylisting'' to kill spam?

Jill points out that the University of Bergen currently operates a "greylisting scheme" for unknown email correspondents.

In brief, their mailservers temporarily reject incoming mail from unknown senders / mail server combinations, relying on RFC2821 (SMTP) error codes to force the sending mailserver to retry 10 minutes later. If the spammer is using hijacked machines, this will most likely not happen; if the sender is a legitimate sender using a standards-compliant mail server, automagic kicks in and the email is delivered as it should (albeit 10 minutes delayed).

I like it.

In theory, this delay could be user configurable depending on the confidence one has in one's whitelist (list of accepted correspondents) thereby increasing the probability of the fraudulent use of a hijacked relaying mail server is discovered and closed down.

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digme: blogg: Spamfiltrering med list og ulempe (May 27, 2004 01:54 PM)
"De fleste spamfiltre har ulemper. Den mest kjente er at ønsket, viktig eller interessant e-post blir borte. Mange av oss bruker filtrering som en administrasjon av tid. Vi filtrerer daglig, men må sette av litt tid nå og da for å sjekke spamsøplek..."

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