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Re: [ietf-smtp] [Shutup] Levels of proposals

2015-12-04 12:15:16
On 12/04/2015 12:10 PM, Steve Atkins wrote:

On Dec 4, 2015, at 9:06 AM, Paul Smith <paul(_at_)pscs(_dot_)co(_dot_)uk> wrote:

The CBL docs say it shouldn't be used for blocking logins, but it may be useful 
to instantly block IPs which are on the CBL and also make a failed attempt to 
login, rather than giving them a few attempts as we normally do. But, given 
that our software is used by businesses for themselves, it may be OK to let 
them just use the CBL(XBL) outright to block logins, as they can easily change 
it if they need to, unlike if it's a huge MSP.

It'd be an additional data source to consider, for sure. But pay close 
attention to Chris's comments about what the CBL/XBL lists and the behaviour to 
expect from those nodes, and be very aware of corporate farms of windows boxes 
behind a single NAT IP.

(I think we're drifting quite a long way from SMTP, let alone where this thread 
started, though :) ).

Heh, yah.  Which I've been replying only to ietf-smtp.

Corporate NAT farms tend not to be as big an issue as you may think, because such things tend to use mail infrastructures of their own, isolated from the NAT, and, having B2B access outside of that (including unrestrained visitors SMTP'ing to random places) tends to be frowned upon. We simply did not permit outbound port 25 from anything but the mail servers even tho we didn't NAT.

Section 7 of the CBL Terms and Conditions gives him an out, his mileage (direct usage or in combination with other information) will vary depending on his environment.

Corporate/organizational (rather than provider) may do quite well without running afoul of the FP caveats. He can but experiment, measure and decide for himself.

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