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](https://docs.vultr.com/how-to-use-sudo-on-a-vultr-cloud-server#create-a-sudo-user-on-debian--ubuntu). * Verify the server has [outbound port 25 open](https://docs.vultr.com/what-ports-are-blocked). 1......