SpamAssassin is an open-source mail filter that identifies spam emails using a wide range of heuristic tests. This guide explains how to install SpamAssassin on Ubuntu 20.04 LTS or 21.04. * Deploy an Ubuntu cloud server instance at Vultr. * Install Postfix mail transfer agent. * Create a sudo user. * Verify the server has [outbound port 25 open](https://docs.vultr.com/what-ports-are-blocked). 1. Connect to your server with SSH. 1. Install SpamAssassin. $ sudo apt-get update $ sud......