A little history... WL2K predates the Winmor sound card system, and originally was only available via Pactor. The early users were predominately blue water sailors who didn't maintain a commercial email-over-radio account. As the system got more popular, land-based stations started using it and the system grew. A friend of mine who is on this forum recommended I try WL2K as an alternative email system and as a peer-to-peer messaging system that enables people to exchange messages without the need for both to be on the radio at the same time.
I started with a Kantronics Kam+ which does Pactor 1 and the system worked very well. My friend and I exchanged messages coast to coast, but the Kam+ does not support scanning so I had to leave my station on a fixed frequency. I would change bands a couple times per day to follow propagation, but it wasn't as convenient as it could have been.
About the time I became sold on the system, many WL2K stations quit accepting P1 connections because their traffic load was increasing and the slow speed of P1 was creating bottlenecks. That was a bummer for me and my Kam+, so I bit the bullet and bought an SCS P2/P3 modem. At that time, Winmor had not been developed and was not an option. The difference between the SCS modem and the Kam+ was truly amazing.
Later, Winmor development reached the point where they went to public testing with only a very few Winmor stations, but by that time I was firmly entrenched in the Pactor world and didn't pay any attention to it. As more time went by, more and more Winmor HF stations went live, until now many of the HF stations are tri-mode capable. Tri-mode means they understand Pactor (P1 - P4), Winmor (500 Hz and 1600 Hz) and Robust Packet. The same station has the equipment and hardware to handle all three protocols interchangeably. Not all RMS stations handle all modes, but many do.
WL2K serves an entirely different purpose than NTS or NTSD; it enables direct one to one communications without involving intermediate station handling. The Winlink people have added tactical callsigns to the mix but I believe those are limited to the public service stations such as may be operated by a local emergency management group. I have not followed the development of these "private" groups.
At one time a group of friends across the country and I experimented with peer-to-peer Pactor linking using the Airmail software that enabled us to maintain very solid contact 24/7. As most experiments go, this eventually faded away and several of the hams sold their SCS modems. Initially, Winmor did not support peer-to-peer connections and only connections to RMS stations were supported. I have heard, but not verified, that Winmor now supports peer-to-peer; if so, that would make it a valuable addition to a prepper's comms toolbox because of the low cost. The ability to receive messages while the station is unattended is very, very nice.
My main interest in email-over-radio was to provide a convenient way to stay in touch with friends without having to keep schedules - particularly when multiple time zones are involved. The ability to do WL2K email as a backup to normal email is a nice bonus.
Wally