Turns out I need to include both libraries.

    <dependency>
      <groupId>org.simplejavamail</groupId>
      <artifactId>simple-java-mail</artifactId>
      <version>8.12.4</version>
    </dependency>
    <dependency>
      <groupId>com.sun.mail</groupId>
      <artifactId>jakarta.mail</artifactId>
      <version>2.0.1</version>
    </dependency>
    <dependency>
      <groupId>org.eclipse.angus</groupId>
      <artifactId>angus-mail</artifactId>
      <version>2.0.3</version>
    </dependency>