TLS/SSL option to connect to a mail server is disabled by the Debian maintainer of this package. Apparently he has an issue with the SSL/TLS licensing and as such he has disabled that option. This is dangerous and for some mail servers is it unsupported.
Package creation based on:
Install (as root):
dpkg -i mail-notification_5.4.dfsg.1-2.2a_amd64.deb