Download james-jpa-smtp-guice-3.8.1.zip from the download page and deflate it.
An usual compilation using maven of this Git repository content will produce two artifacts into server/container/guice/jpa-smtp/target directory :
To run james, you have to create a directory containing required configuration files names conf.
A sample directory is provided with some default value you may need to replace.
Edit the configuration to match your needs.
You also need to generate a keystore with the following command :
$ keytool -genkey -alias james -keyalg RSA -keystore conf/keystore
Once everything is set up, you just have to run the jar with :
$ java -javaagent:james-server-jpa-smtp-app.lib/openjpa-3.2.0.jar \
-Dworking.directory=. \
-Djdk.tls.ephemeralDHKeySize=2048 \
-Dlogback.configurationFile=conf/logback.xml \
-jar james-server-jpa-smtp-app.jar