ANNOUNCE: BarricadeMX is released

Steve Freegard steve.freegard at
Thu Jun 14 23:21:33 IST 2007

Hi Phil,

--[ UxBoD ]-- wrote:
> As MailScanner parses the message then it should be fairly easy to write
> the to_address to a file, or even hold it as a global hash shared between
> the perl processes.  When the recipient replies, if they do, then the hash
> could be checked and allow the message through without any checks.  Or if
> using a file the whitelisted entry can be looked up.
> A hash value could be created for the time the message was sent including
> the to_address, and then reversed on its way back in.  If within a
> pre-determined time it passes through okay, or it has the normal checks
> applied.

This sort of thing could easily be written as a Custom Function applied 
to the 'Is Definitely Not Spam' option - but there are definitely a few 
issues to consider when using a method like this as this was something 
we considered when we were developing BarricadeMX.

It requires some sort of backing store to be effective as you need to 
keep the data around for a while for it to be effective (BarricadeMX 
allows for auto-whitelisting for 7 days by default and this is 
adjustable), this data also needs to be shared amongst multiple gateways 
if you have them (which would then require a proper database).  Things 
like BATV, SRS, VERP, Out-of-Office replies and autoreponders also cause 
issues when you are attempting to auto-whitelist anyone that your users 
have sent mail to and you leave yourself open to sender address spoofing 
during the auto-whitelist period.

In BarricadeMX we came up with a very clever way to handle this and 
backscatter prevention at the same time without the need for a database 
  or the tracking of senders/recipients and is one of the things we 
decided to patent so our competitors couldn't steal the idea.  Because 
of this we can't offer this functionality natively for MailScanner (as 
Julian already said on the -beta list).

Kind regards,

Steve Freegard
Development Director
Fort Systems Ltd.

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