How to Enable Tarpitting to Reduce Spam

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Tarpitting is when a server identifies a client’s abnormal email operations, and slows down or “tarpits” the process, preventing spam. For more information:

 With tarpitting enabled, if a sender attempts to issue commands to the mail server before the banner, the connection is dropped:

[root@localhost ~]# telnet 25
Connected to
Escape character is ‘^]’.
HELO test
554 SMTP protocol violation
Connection closed by foreign host.

Set Up:

To enable tarpitting, follow these steps:


  1. At the command line, use the text editor to view /etc/tcprules.d/tcp.smtp. It will look similar to the following:

2. At the end of the line beginning with :allow, add the following: ,GREETDELAY="5",DROP_PRE_GREET="1"

3. Run ~vpopmail/bin/clearopensmtp



Aug 23, 2017, 3:03 pmBy: InterWorx
How to Enable Tarpitting to Reduce Spam
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