Greylisting Addon

UxBoD uxbod at
Wed Nov 28 15:48:51 GMT 2007

Come on Steve not another plug ;) Sounds good though :)


--[ UxBoD ]--
// PGP Key: "curl -s | gpg --import"
// Fingerprint: C759 8F52 1D17 B3C5 5854  36BD 1FB1 B02F 5DB5 687B
// Keyserver: Key-ID: 0x5DB5687B
// Phone: +44 845 869 2749 SIP Phone: uxbod at

----- Original Message -----
From: "Steve Freegard" <steve.freegard at>
To: "MailScanner discussion" <mailscanner at>
Sent: Wednesday, November 28, 2007 3:33:33 PM (GMT) Europe/London
Subject: Re: Greylisting Addon

shuttlebox wrote:
> On Nov 28, 2007 1:13 PM, Michael Mansour <micoots at> wrote:
>> Yes it is a memory hog, but 400Mb of virtual memory isn't that much
>> considering I have over 72,000 auto-managed records per server.
> It's also easy to tune the memory consumption by adjusting how long it
> will keep grey/whitelisted entries in the database.
>> I have tried others and found they may work well for one server, but not in
>> a distributed environment which requires sync between MX servers.
> The sync is very important and I haven't found an alternative that is
> capable of that.

BarricadeMX's greylisting mechanism has a far better system for cache 
synchronization between peers than milter-greylist, it uses multicast 
UDP for local peers and unicast UDP for remote peers and doesn't need 
any nasty MySQL replication etc. (it uses a local SQLite database).  It 
also uses less memory as it doesn't hold all the records in memory...

I am biased as I helped develop it, but the greylisting algorithm is 
also better than any of the other greylisting implementations as it 
requires far less whitelisting (only servers that *never* retry need to 
be bypassed - shared spools are not a problem) and it doesn't penalize 
different sender/recipient pairs if the server has already proven that 
it correctly implements a retry queue (which is the point of greylisting 
after all).  The version that we are about to release also contains a 
secondary greylist algorithm which is 100% accurate against some of the 
more persistent botnet spam that creeps through traditional greylisting.

Oh - and did I mention that it works with any MTA (as it's an SMTP 
proxy) and that MailScanner automatically detects that it is in use and 
modifies it's behavior to accommodate it?  ;-)


Steve Freegard
Development Director
Fort Systems Ltd.
MailScanner mailing list
mailscanner at

Before posting, read

Support MailScanner development - buy the book off the website! 

This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.

This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.

More information about the MailScanner mailing list