My best bet would be: When using MIME, you are the one responsible for the stuff you inside the MIME header, Domino does not care, just sends it off. When you use the "old way" Domino will lookup the person in the NAB, and check whether it should be routed inside the Notes domain (keep the Notes name) or outside (use internet naming format)
Author: Oliver Busse
http://about.me/oliverbusse
This software is licensed under the Apache License 2.0
Code snippets or any other console output - if not otherwise proclaimed - licensed under WTFPL – Do What the Fuck You Want to Public License
Made with love and IBM XPages, using Twitter Bootstrap 3
This website uses the XPages Extension Library, Bootstrap4XPages Plugin and the OpenNTF Domino API