greylistd software package provides Greylisting daemon for use with Exim 4, 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 greylistd
greylistd is installed in your system.
Make ensure the greylistd package were installed using the commands given below,
$ sudo dpkg-query -l | grep greylistd *
You will get with greylistd package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | |
| Package | greylistd |
| Version | 0.8.8.7 |
| Description | Greylisting daemon for use with Exim 4 |
| Sub Section |