Rspamd is described as 'advanced spam filtering system that allows evaluation of messages by a number of rules including regular expressions, statistical analysnd custom services such as URL black lists'. There are six alternatives to Rspamd for a variety of platforms, including Linux, Self-Hosted solutions, SaaS, Online / Web-based and Mac. The best alternative is SpamAssassin, which is both free and Open Source. Other great apps like Rspamd are Proxmox Mail Gateway (Paid, Open Source), MailScanner (Free, Open Source), Scrollout F1 (Free, Open Source) and EuropeanMX (Paid).
Use this program to "Unspam" your mailbox(es). The program can be integrated with the mail server to automatically filter all mail for a site. It can also be run by individual users on their own mailbox and integrates with several mail programs.
MailScanner is a open source email security system design for Linux-based email gateways. It is used at over 30,000 sites around the world, protecting top government departments, commercial corporations and educational institutions.
EuropeanMX blocks incoming spam and virus emails before they are reaching your network. With our outgoing filter you can secure your server's reputation. And last but not least we are offering encrypted cloud storage to archive all your emails.