Re: [Asrg] Some data on the validity of MAIL FROM addresses

[Yakov Shafranovich <[e-mail]>]

At 05:17 PM 5/18/2003 -0600, Vernon Schryver wrote:
>[...]
>Are you expecting not only that distant users will respond to challenges,
>but that their ISPs will modify their MTAs to maintain databases of
>all addresses to which their users have sent mail?  If so, that
>seems...implausible.

I did expect ISPs to maintain such databases for only for a limited time. 
An average challenge/response interaction if done by automated software 
only takes moments or at most minutes. If an ISP is implementing an 
automated C/R system, they might keep track of outgoing addresses just like 
they keep a whitelist and queue for incoming. However, that would be an 
optional part of the draft.

What I do expect is that users will not reply to challenges that come from 
strangers - if spammers start using someone's email address for the "FROM" 
field, it would make sense to assume that the user in question will not 
respond to thousands of incoming messages.

Yakov 

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