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Article: 878
From: H. Loeung
Date: 2006-04-03 21:58:43 -0400
Subject: Re: milter-sender - Greylisting and blind MX server checking

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Hello Anthony,
On Mon, 30 Jan 2006 04:38 pm, I wrote: 
> My understanding of milter-sender's use of greylisting is that it is
> applied to MX servers that appears to accept mail for any e-mail
> address. Greylisting is enabled by default and could be disabled by
> setting CacheGreyListTTL to 0.
> How milter-sender determines if an MX server blindly accepts mail is by
> generating an intentionally false e-mail address and using it to see if
> the MX server will accept mail destined for this address.
> I was just wondering, with greylisting disabled (CacheGreyListTTL set to
> 0), is there any reason why we still check to see if an MX server
> blindly accepts mail?

I'll try and explain what I meant better. An example SMTP callback that 
milter-sender performs is as follows:

1.  S: 220
2.  C: HELO mail1.myserver.com
3.  S: 250
4.  C: MAIL FROM:<>
5.  S: 250
6.  C: RCPT TO:<TRAPLACOL0@example.com>
7.  S: 550
8.  C: RSET
9.  S: 250
10. C: MAIL FROM:<>
11. S: 250
12. C: RCPT TO:<localpart@myrealbox.com>
13. S: 250
14. C: QUIT
15. S: 221

From the above, you can see that there are two tests being performed by 
milter-sender. The first, as indicated by lines 4-7, tests to see if an MX 
server blindly accepts mail.

The second, as indicated by lines 10-13, actually tests to see if our 
sender does exist.

My question is, with greylisting disabled (CacheGreyListTTL set to 0), does 
it seem like a good idea to disable the first test?


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