I am trying to bind the @Resource(name="mail", type=Session.class) to JNDI resource name specified in JBoss mail-service.xml (here it is <attribute name="JNDIName">java:/mail</attribute>

I don't have a control over editing annotation tag (it would work fine with mappedName="java:/mail" ) because it is running on different server in production and I am here running the TestNG test case on embedded JBoss.

from log file -
mail is bound to:
[org.jboss.mail.MailService.bind():356] Mail Service bound to java:/mail

but it complains:
you did not specify a @Resource.mappedName() on javax.mail.Session ca.gc.cida.pac.reminder.ReminderAction.mailSession and there is no binding for enc name env/mail/hope in XML