Mautic

Mautic is an open-source marketing automation platform with full email campaign and contact management capabilities. You can run it self-hosted on your own infrastructure or use their cloud version, giving you control over your data and operations. It tracks visitor behavior, manages automation workflows, and sends targeted emails based on subscriber actions and attributes.

Mautic suits organizations that need powerful automation but want to avoid vendor lock-in or recurring per-contact fees. It's more complex than lightweight plugins but doesn't require the budget or commitment of enterprise platforms like HubSpot, and the WordPress plugin integration simplifies email signups directly from your site.