When visiting https://lists.gnupg.org/ , firefox says:
lists.gnupg.org uses an invalid security certificate. The certificate expired on September 19, 2017, 2:07 PM. The current time is September 19, 2017, 4:46 PM. Error code: SEC_ERROR_EXPIRED_CERTIFICATE
there doesn't seem to be a lists.gnupg.org infrastructure tag, or i would add it to this ticket.