Getting Started with Winlink and WINMOR — this is a VERY complete work.
From the intro page
WINMOR stands for WINlink Message Over Radio and is a new HF radio transmission protocol by Rick Muething, KN6KB, of the Winlink Development Team. WINMOR was introduced at the 2008 ARRL / TAPR Digital Communications Conference in Chicago on September 26-28, 2008, and released from beta testing to production versions in 2010. Unlike PACTOR, only a simple computer soundcard-to-radio interface is required, and it runs as a “virtual TNC” (the WINMOR TNC application) together with host software. The protocol (not the software source code) isfully documented and is without restrictions or license issues which might prevent anyone from implementing the protocol in other software. The WINMOR TNC software is also fully documented as an API for developers. The software TNC can be freely distributed when paired with a developer’s own host application software.
Special RMS stations without internet
A special type of station can be a hub acting as a central mailbox for delivery and pickup of messages when no internet connection is available. For our area we have N5TW as an “MPS” (Message Pickup Station) type of connection. Be sure to configure that in your RMS Express system — see someone about how to do that.