There are currently three mailing lists related to nmh:

nmh-announce@nongnu.org
-----------------------
This is a very low-traffic mailing list for announcing new releases,
patches, and important events related to nmh.

To subscribe or manage your subscription options, go to:
  https://lists.nongnu.org/mailman/listinfo/nmh-announce


nmh-workers@nongnu.org
----------------------
This is the main list for discussing work on nmh.  There is currently
no nmh-users mailing list, so user questions are acceptable here (the
comp.mail.mh newsgroup is another good option).  Bug reports and
feedback should be submitted here.

To subscribe or manage your subscription options, go to:
  https://lists.nongnu.org/mailman/listinfo/nmh-workers


nmh-commits@nongnu.org
----------------------
All commits to the nmh source code repository are copied to this list.
Therefore, it is probably only of interest to nmh developers.

To subscribe or manage your subscription options, go to:
  https://lists.nongnu.org/mailman/listinfo/nmh-commit


mail archives
-------------
The nmh-workers and nmh-commits mailings lists archives are available here:
  http://lists.nongnu.org/archive/html/nmh-workers/
  http://lists.nongnu.org/archive/html/nmh-commits/