Compatible with version
No compatibility info given!
The plugin checks subscription emails for spam using the Botbouncer class https://github.com/michield/botbouncer. It currently uses only the Stop Forum Spam service to check email addresses, as that can be used without registering. The other services supported by Botbouncer (Akismet, Project Honeypot, and Mollom) could be added if Stop Forum Spam proves not to be sufficient.
See the README file on the GitHub page https://github.com/bramley/phplist-plugin-botbouncer