BillionMail
The self-hosted email marketing platform with a built-in MTA. A high-risk, high-reward alternative to Mailchimp that offers unlimited sending but requires strict governance oversight.
Listmonk
A high-performance, self-hosted newsletter and mailing list manager that provides enterprise-grade mass-mailing capabilities without the recurring per-subscriber tax.
Thunderbird
The open-source standard for email, calendar, and contacts. Revitalized with the 'Supernova' interface and built for privacy and ownership.