Haraka SPF Plugin

This package, `haraka-plugin-spf`, implements the Sender Policy Framework (SPF) within the Haraka SMTP server. The current stable version is 1.2.11. It primarily adds `Received-SPF` headers to emails, with robust configurable options to defer or deny mail based on SPF test results, such as `mfrom_fail` for sender validation. While it has seen consistent updates recently, including ES6 refactoring, dependency bumps, and header formatting improvements, it does not adhere to a strict time-based release cadence, focusing instead on bug fixes and enhancements. Its key differentiator is its deep and flexible integration into the Haraka ecosystem, allowing granular control via `spf.ini` for handling various SPF outcomes (none, softfail, fail, permerror) for both HELO and MAIL FROM contexts, and specifically for relayed connections. It also provides a valuable command-line tool for debugging SPF records and validating domain configurations. The plugin allows Haraka operators to enforce SPF policies ranging from mere informational headers to hard rejections, providing essential protection against email spoofing.