dccifd / greylisting problems

[Smart,Dan]

PMJI:
The negative of greylisting is that some "legit" mail servers may give up
after one attempt.  These will need to be whitelisted to bypass greylisting.


Also, there is a long discussion on DCC list on functionality, and it
appears that an initial denial of 1 - 3 minute(s) is sufficient to stop most
Spam senders, who send once then forget.  Most users would not see this
delay.  Whitelisting will still be an issue for broken sites.

Greylisting needs to run at the mail MTA, so that messages get blocked
*before* they are accepted by your mail MTA.  That's the whole idea... Block
messages once before accepting them the second time.

Each message records a tuple in DCC:  The sender, recipient, and IP address
of sending MTA.  After being saved the first time, every time this recorded
tuple is seen, the message gets delivered immediately. The tuples have a
time-to-live, and will expire off the DCC server eventually.

<<Dan>>




>  -----Original Message-----
>  From: MailScanner mailing list
>  [mailto:MAILSCANNER at JISCMAIL.AC.UK] On Behalf Of Matthew Henkler
>  Sent: Saturday, July 31, 2004 10:03 PM
>  To: MAILSCANNER at JISCMAIL.AC.UK
>  Subject: Re: [MAILSCANNER] dccifd / greylisting problems
>
>  On Sat, 31 Jul 2004, John Rudd wrote:
>
>  > But I think it's more of a sendmail milter type thing than a
>  > mailscanner thing.  By the time mailscanner sees the
>  message, it's too
>  > late to reject it for the sender to try again later.
>
>  Yes, that seems likely now that I think about it.  The way I
>  have it set up at least, it is  most likely too late for
>  MailScanner to do anything about.  Guess I'll have to play
>  around with it at the MTA level.
>
>  Good explanation of greylisting for everyone though, thanks!
>
>  matt
>
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>

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