Spark Mail - Spark helps you take your inbox under control. Instantly see what’s important and quickly clean up the rest. Spark for Teams allows you to create, discuss, and share email with your colleagues
SpamAssassin - Use this program to "Unspam" your mailbox(es).
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
Newton Mail - Newton is a fully featured mail client available for Android, iOS, macOS and Windows.
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...