Validating Email addresses

[Eli Wapniarski]

On Tuesday 05 May 2009 20:55:43 Paul Lemmons wrote:
> We are getting a great deal of Spam bypassing both Postini and Mail 
> Scanner due to a discrepancy between how these two products define an 
> email address and the way Exchange does. The two scanning products 
> recognize emails with a pipe character "|" at the beginning of the 
> address as both valid and part of the email address. I believe this is 
> in line with the email standards. Exchange, othe the other hand simply 
> ignores the character. So a message sent to me at mydom.com and 
> |me at mydom.com are seen as two different addresses by the scanning 
> systems and as a single address by Exchange.
> 
> I have tried with minimal success to check for the pipe using sendmail 
> rules. I have it stopped but it is stopping more than it should. I would 
> like to stop it with MailScanner. I have tried what appears to be 
> obvious to me but so far I have not hit upon the magic combination of 
> options to make this work. Has anyone else encountered this situation 
> and come up with a solution?
> 

Yes, I have. And my solution is to run milter-regex to filter legit and illegit email addresses.

If you install the milter, then feel free to use the following macro to filter out legit and illegit email addresses. Of course you will need to substitute email at address.one, etc for real email addresses. Hopefully your distro will have milter-regex available. However if not, then you can find it at:

http://www.benzedrine.cx/milter-regex.html

It took me quite some time to get the regular expressions to work the way I wanted because I am by no means an expert with regular expressions. And its been so long since I needed to look up and understand the syntax. However, the following works and it works very well. 


IllegitimateTo = header /^TO$/i /(\.email at address.one\>|\.email at address.two\>|\.email at address.etc\>|)/e
LegitimateTo = header /^TO$/i /(\<email at address.one\>|\<email at address.two\>|\<email at address.etc\>)/e
LegitimateFrom = header /^FROM$/i /(email at address.one|email at address.two|email at address.etc)/e
LegitimateMail = $LegitimateTo or $LegitimateFrom
discard not $LegitimateMail
discard $IllegitimateTo

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