Magnolia 5.4 reached end of life on November 15, 2018. This branch is no longer supported, see End-of-life policy.
Mail explains how to configure the module and how to send mail from Magnolia.
<dependency> <groupId>info.magnolia</groupId> <artifactId>magnolia-module-mail</artifactId> <version>5.3</version> </dependency>
You will also need mail-1.4.5.jar for the module to work correctly.
See Mail.