This profile option specifies the host and port of the Web server that notification mailers use to generate the content for Oracle Applications Framework regions that are embedded in notifications. If this profile option is not set, notification mailers will use the same Web agent specified in the Application Framework Agent profile option.
I'm writing this because, there is no recorded bugs for this issue for EBS 12.2. (Actually there are bugs records and fixes for these types of problems which may be encountered in earlier releases)
Look at the real life example below;
Error log entry in Notitication mailer's log file:
oracle.apps.fnd.wf.mailer.NotificationFormatter.getFormattedMessages()]:Problem parsing XML -> org.xml.sax.SAXException: Problem obtaining the RESOURCE content -> java.net.MalformedURLException: For input string: "8000 "