I had to manually install libnet-ssleay-perl libcrypt-ssleay-perl libio-socket-ssl-perl to get TLS to work.
$ lsb_release -sdc Ubuntu 16.04.6 LTS xenial
$ apt-cache depends sendemail sendemail Depends: perl Depends: libio-socket-inet6-perl Suggests: libio-socket-ssl-perl Suggests: libnet-ssleay-perl
I had to manually install ssleay- perl ssl-perl
libnet-ssleay-perl
libcrypt-
libio-socket-
to get TLS to work.
$ lsb_release -sdc
Ubuntu 16.04.6 LTS
xenial
$ apt-cache depends sendemail inet6-perl ssl-perl
sendemail
Depends: perl
Depends: libio-socket-
Suggests: libio-socket-
Suggests: libnet-ssleay-perl