The projects on which Kit FreeMiNT is based each have their own mailing list.

 FreeMiNT

The list is hosted at sourceforge.

 The short-lived list

A short-lived list (may 2016 to october 2017) is available here.

 Archive of the old list

The old mailing list (january 1993 to march 2016) is here.

EmuTOS

The list is hosted at sourceforge.

ARAnyM

The mailing list, intended for both developers and users, is hosted on Google Groups.

FreeGEM

The PC version of GEM still has a mailing list. It can be accessed here.