Winlink-Mac: Internet Email over Radio on a Mac
This is Ki7QFV with a basic how-to in getting a Mac Laptop to work with Winlink Express over RF. To do this you'll be installing Wine/Homebrew and WinlinkExpress. You'll see lots of errors, just continue through the process.
In my example, I used a TNC-X from Coast Communications, a USB cable, over a 1200 baud serial connection. But the same basic concept should also work for bluetooth. Note I had to force the serial port speed to 1200 baud because that's how my TNC-X came configured... although that can be changed.
Ignore the packet/bluetooth comments, this still applies to winlink over USB. Ray Rischpater, KF6GPE put the original how-to together for a TH-D74 and bluetooth, and I've revised it to support Winlink for a TNC-X (and hopefully a Signalink)
Summary of steps: (and do this with a FAST internet connection - lots to download.
0) Make sure the Mac driver is already installed for your serial device! For my TNC, I went here: 
1) Install Homebrew
a) open terminal b) run /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
2) in the same terminal window, type:
a) brew install wine && brew install winetricks b) WINEARCH=win32; export WINEARCH c) winetricks dotnet35sp1
3) open a new terminal window (so you have 2 windows to look at). These steps will link your Mac driver to Winlink Express.
a) cd /dev b) ls c) **look at the list - which one looks like it has the word serial in it?** substitute that in line e below d) cd ~/.wine/dosdevices e) ls -s /dev/cu.usbserial-#### com2
4) in your other terminal window
a) edit the ~/.wine/system.reg file and make sure it has the following lines in it
[Hardware\\Devicemap\\Serialcomm] 1231984861 #time=1c976b51d546c80 "Serial1"="COM2"
5) download RMSExpress and unzip the windows installer - so you have an MSI to work with. Remove spaces from the name!
6) in either of your terminal windows, change to the msi directory location and type the following
a) wine msiexec /i RMSExpressSetup.msi b) wine ~/.wine/drive_c/RMS\ Express/RMS\ Express.exe (or whatever location on the virtual C drive that you used)
7) Pick telnet winlink, open session, and then click start. Make sure your basic winlink configuration is correct.
8) then pick Packet Winlink, Normal, Com2 for the serial port, and 1200 for the baud rate.
9) to get a list of local winlink packet channels, you may need to download them. Make sure you've configured your grid square. There's a bug - choose *update table via radio* - and then use telnet to fetch the list over the internet.
10) Switch back to packet winlink, choose your channel, and set your radio frequency to match!
11) Send yourself a winlink message, and check it out on the winlink webmail page, to see if it's working.