Mailx

# apt-get install heirloom-mailx
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  s-nail
The following NEW packages will be installed:
  heirloom-mailx s-nail
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 350 kB of archives.
After this operation, 715 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://deb.debian.org/debian stretch/main amd64 s-nail amd64 14.8.16-1 [340 kB]
Get:2 http://deb.debian.org/debian stretch/main amd64 heirloom-mailx all 14.8.16-1 [9,640 B]
Fetched 350 kB in 0s (1,169 kB/s)    
Selecting previously unselected package s-nail.
(Reading database ... 37742 files and directories currently installed.)
Preparing to unpack .../s-nail_14.8.16-1_amd64.deb ...
Unpacking s-nail (14.8.16-1) ...
Selecting previously unselected package heirloom-mailx.
Preparing to unpack .../heirloom-mailx_14.8.16-1_all.deb ...
Unpacking heirloom-mailx (14.8.16-1) ...
Setting up s-nail (14.8.16-1) ...
Processing triggers for man-db (2.7.6.1-2) ...
Setting up heirloom-mailx (14.8.16-1) ...