The e-mail service can use any SMTP account configured in $JBOSS_HOME/server/default/conf/gatein/configuration.properties (or $TOMCAT_HOME/gatein/conf/configuration.properties if you are using Tomcat).

The relevant section looks like:

# EMail
gatein.email.smtp.username=
gatein.email.smtp.password=
gatein.email.smtp.host=smtp.gmail.com
gatein.email.smtp.port=465
gatein.email.smtp.starttls.enable=true
gatein.email.smtp.auth=true
gatein.email.smtp.socketFactory.port=465
gatein.email.smtp.socketFactory.class=javax.net.ssl.SSLSocketFactory

It is preconfigured for GMail, so that any GMail account can easily be used (simply use the full GMail address with username and password.

In corporate environments, if you want to use your corporate SMTP gateway over SSL, like in the default configuration, configure a certificate truststore containing your SMTP server's public certificate. Depending on the key sizes, you may then also need to install Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files for your Java Runtime Environment.