Re: [exim] Greylisting - using Exim new features - ratelimit…

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Autor: Martin A. Brooks
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A: Marc Perkel, Exim users mailing list
Assumpte: Re: [exim] Greylisting - using Exim new features - ratelimit with noupdate
Marc Perkel wrote:
> The idea behind this is that it requires the server be touched twice in
> the proper order to get in. Spam bots try once and not in the proper
> order. That's how the filter works.


This is, effectively, an implementation of port knocking, a security
practice I have yet to be convinced is worth the effort. I'm wondering
how your implementation will deal with perfectly legitimate email coming
from the many many SMTP sending engines that don't follow the standards.


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