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January 14, 2006



Nice write-up, Steve. As soon as I get my new colo solution up and get mail running I'm going to partake of this goodness as well.

I guess the simple counter for spammers would be to find a magic number (interval time) and send a second email within that timeframe? Why *wouldn't* they do precisely this -- especially after greylisting gets popular.


I run postgrey/postfix too. If greylisting comes into really wide use I imagine a lot of spammers *will* just start running "real" mailservers that retry in the usual way. Greylisting could still be helpful in that scenario, since some of those servers will get shut down or blacklisted within the retry window, but it won't be magic like it is now.

Mei Adja

Nice article sir. I know that mail server is much different than when you write this. However, can you tell me what is the minimum specification for mail server?

Best regards
Terapi Diabet

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  • Steve Friedl is a software and network security consultant in Southern California. He has been a C and UNIX developer since 1981 and has an exceptionally broad background in this area. Some areas of expertise include:

    • C and C++ systems software development on the UNIX and Win32 platforms
    • Communications, including serial and TCP/IP based controllers
    • Enterprise internet security administration and configuration
    • Penetration tests, audits, and network reviews
    • Security forensics, reverse engineering, and tools development
    • General UNIX and Windows system/network administration
    • The Windows Printing System
    • Database software development
    • Technology problem solving and research
    • Technical writing and standup training

Unix Wiz

Stephen J. FriedlSoftware ConsultantOrange County, CA USASteve@unixwiz.net