Airmail is a fantastic program for diagnosing Packet/packtor - Comport issues.
it is also good to clear failures Initializing a TNC

Using Windows 11 and Airmail I started to see problems like slow responding to commands or a "Not Responding" error being displayed.

If that occur then  you will need to do the following:

Using File Manager go to the "Airmail" folder and locate the Airmail3.exe file

Right mouse on it and choose "Properties"

Click on "Compatability"

Now click on the "Run this program in compatability mode for:"
Now  click on "Windows 7" then "Apply"  and "OK"

It should look like this...and Airmail is ready to use.