SpamAssassin - Use this program to "Unspam" your mailbox(es).
TinyWall - Lightweight and non-intrusive firewall
MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
GlassWire - Visualize network activity in detail, get notified when new apps access the network, look out for...
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
Windows Firewall Control - Windows Firewall Control is not the built in firewall system in the Windows operating systems.