Invalid requests for SMTP receive connectors

Some participants on the Internet try to overload other email servers by sending invalid requests (so-called denial-of-service attacks) or exploit security holes to break into servers. In order to minimize these attacks, you can specifically slow down such requests, for example by using the so-called tarpitting.

Settings for invalid requests when configuring SMTP receive connectors

Behaviour when receiving invalid SMTP commands

Tarpitting Tarpitting is a method of slowing down email relays that do not adhere to the RFC when it comes to SMTP command sets and/or their correct order. As soon as an SMTP command is transmitted incorrectly or in the wrong place, NoSpamProxy waits five seconds with its response for every other command. The transmission of commands is thus artificially made more difficult, as if you were taking a path through a tar pit - hence the name tarpitting.

With the slider for the tarpitting level you can set by how many seconds NoSpamProxy Protection delays the response. If you set the slider to Low, the gateway will wait 2 seconds. Medium results in a 5 second delay and High results in a 10 second delay.