Re: [exim] automatically blacklisting clients that fail SMT…

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Autor: Mikhail Lischuk
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A: exim-users
Assumpte: Re: [exim] automatically blacklisting clients that fail SMTPauthentication


On Thu, 09 Jun 2011 16:38:10 +0000, W B Hacker wrote:

> Smart

folks, and they'll probably not be among the 18 Ukrainian .tld I hard
block who DON'T try to curb the worst of their WinBots.

Sorry for
off-topic posting, but let me clarify a little about Ukrainian ISPs:
most of them have a marketing approach of "providing clean unfiltered
Internet" to their clients, that's why they don't block 25 port. The
largest cable and ethernet ISPs that come to my mind do not filter 25
port.

Second - if you block 25 port, it's a good approach to provide
some kind of smarthost for your clients. Which will be in turn used by
bots in all ways they want and smarthost will be blacklisted very often
- maybe sometimes entire subnet. Besides if you implement some ways of
blocking problem clients on your smarthost, you will greatly increase
load average for your helpdesk.

So, blocking 25 port is a good
approach for ISP, but it will not make them spam- or problem-free.

--

With Best Regards
Mikhail Lischuk [1]

ITX Ukraine




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[1] mailto:mlischuk@itx.com.ua