Declaring a JavaMail Resource

The basics are that any properties listed in the <Resource> element are given directly to the javamail provider via javax.mail.Session.getDefaultInstance(Properties props).

Here might be some example properties.

<Resource id="SuperbizMail" type="javax.mail.Session">
   mail.smtp.host=mail.superbiz.org
   mail.smtp.port=25
   mail.transport.protocol=smtp
   mail.smtp.auth=true
   mail.smtp.user=someuser
   password=mypassword
</Resource>

You can create as many <Resource> entries like this as you wish, they just have to have a unique 'id'.

Careful not to add whitespace at the end of your property values. A java.util.Properties object will leave those in the property values and they will be passed to the JavaMail provider with the whitespace on the end which may cause issues if the provider does not actively trim the values before attempting to use them.

Overriding

If you wanted to do a System property or InitialContext property override of the above example mail session, you could do so like this:

java ... -DSuperbizMail.mail.smtp.host=localhost