Self-Hosted Event RSVP Tools

Listmonk is a self-hosted email marketing platform and newsletter manager designed for high-volume bulk email distribution and transactional messaging. It provides a centralized system for organizing large subscriber databases and executing automated marketing campaigns directly from your own infrastructure. The platform distinguishes itself through its reliance on a relational database backend, which enables dynamic subscriber segmentation using complex query filtering at the time of delivery. It utilizes a concurrent worker pool to manage high-throughput email dispatch and incorporates a server-side template engine to inject personalized subscriber data into communications before they are sent. Beyond core list management, the system supports the orchestration of transactional emails and automated newsletters through integration with standard mail delivery providers. It exposes a stateless interface for programmatic control over campaigns and subscriber data, allowing for external system integration. The application is distributed as a single static binary, which simplifies deployment by removing the need for external dependency management on the host server.

Plunk is an SMTP email marketing platform and contact relationship manager used for sending bulk broadcasts and transactional emails. It provides a transactional email API for delivering personalized messages using templates and variable substitution, supported by built-in analytics and custom domain authentication. The platform features an email automation workflow engine with a visual builder for creating multi-step sequences triggered by user events and conditional logic. It includes a dynamic audience segmentation tool that groups contacts based on real-time data attributes and behavioral patterns. The system manages contact databases through a relational data store that tracks full user activity history and unifies interactions from campaigns and workflows. It covers a broad range of delivery and monitoring capabilities, including SMTP relay services, inbound email processing via webhooks, and delivery analytics for tracking open and click-through rates. Security is handled through custom domain authentication, enabling the management of DKIM and SPF records to verify sender identity.

Cal.com is a comprehensive scheduling infrastructure platform designed to manage availability, booking workflows, and calendar synchronization across multiple users and external services. It provides a backend service for automated appointment scheduling, enabling the creation, confirmation, and management of booking lifecycles through a centralized state machine. The platform also offers embeddable user interface components that allow developers to integrate interactive booking experiences directly into third-party websites. What distinguishes the platform is its extensible app ecosystem and intelligent automation capabilities. Developers can build custom integrations using a modular plugin architecture, while an AI-driven interface allows for complex scheduling operations and configuration updates via natural language commands. The system includes a sophisticated event routing engine that automatically assigns meetings to hosts based on availability, round-robin rules, and organizational hierarchy, supported by real-time webhook orchestration to keep external systems synchronized. The platform covers a broad capability surface including CRM data synchronization, granular role-based access control, and secure OAuth-based integration management. It supports advanced booking configurations, such as prefilling form data and monitoring state changes, alongside specialized tools for Salesforce connectivity, including assignment traceability and fuzzy account matching. Users can also leverage local or remote server hosting options to maintain control over their infrastructure and security configurations.