Note

You are viewing the documentation for an older release of Interworx (6.x). To see documentation for the current generally available release of Interworx, click here: 7.13.

How to Enable Tarpitting to Reduce Spam

Tarpitting is when a server identifies a client’s abnormal email operations, and slows down or “tarpits” the process, preventing spam. For more information: https://www.techopedia.com/definition/1722/tarpitting.

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

[root@localhost ~]# telnet test.corp.interworx.com 25
Trying 10.1.16.999...
Connected to test.corp.interworx.com.
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:

    Tarpitting 1

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

    Tarpitting 2

#. Run ~vpopmail/bin/clearopensmtp