courier-pop-ssl software package provides Courier mail server - POP3 over SSL [transitional], you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install courier-pop-ssl
courier-pop-ssl is installed in your system.
Make ensure the courier-pop-ssl package were installed using the commands given below,
$ sudo dpkg-query -l | grep courier-pop-ssl *
You will get with courier-pop-ssl package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | |
| Package | courier-pop-ssl |
| Version | 0.76.3-1 |
| Description | Courier mail server - POP3 over SSL [transitional] |
| Sub Section |