Sunday, 1 June 2008

Add a new regex string and keep your fingers crossed!?

WARNING: The information presented in this article is provided without warranty. Use at your own risk! Do not implement any features without full understanding of the implications. Using these measures incorrectly MAY prevent e-mail from reaching your server.

Whilst testing a complex regex string is a must, you can never tell if it is correct or, Postfix won't throw a hissing fit when it is live. Hard as you try to, you never know if a string will accidently block legitimate mail.

I run my own personal server for self experimentation and, the only users are family members. If you can, put a new string on a test server first. Always keep an eye on your logs, to see what is getting blocked by a new string. If unwanted mail is still reaching your mail client application, fine tune the string but a keep a copy of the previous string below it.


# rolex or cartier
/([rR][-\. ]?[oO0][-\. ]?[lL][-\. ]?[eE][-\. ]?[xX][\.\? ]?)|([cC][-\. ]?[aA4][-\. ]?[rR][-\. ]?[tT][-\. ]?[iI1][-\. ]?[eE][-\. ]?[rR][\.\? ]?)/ REJECT Message body rejected [101]

# rolex
/[rR][-\. ]?[oO0][-\. ]?[lL][-\. ]?[eE][-\. ]?[xX][\?\. ]?/ REJECT Message body rejected [102x]
/[rR][oO0][lL][eE][xX]/ REJECT Message body rejected [102]

# cartier
/[cC][-\. ]?[aA4][-\. ]?[rR][-\. ]?[tT][-\. ]?[iI1][-\. ]?[eE][-\. ]?[rR][\.\? ]?/ REJECT Message body rejected [104x]
/[cC][aA4][rR][tT][iI1][eE][rR]/ REJECT Message body rejected [104]

Here, I have amalgamated my rolex and cartier strings into one. Until I am happy with it, I have the separate strings below it. In fact, whilst I was testing the new cartier string, I kept a basic string below it. Just to make sure that I still blocked some junk! Note that anything after the REJECT is just a textual string for your log/s. Numbering the strings helps, when checking your log/s, to show which strings are working the best.

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