phpList

phpList is a mature, open‑source email marketing engine written in PHP that enables developers to host, customize, and scale full‑fledged newsletter campaigns. At its core it functions as a message queue with sophisticated routing, bounce handling, and analytics, all exposed through RESTful APIs, CLI tools, and a web UI. The platform has been in production for over a decade, delivering more than 25 billion emails in 2018 and serving users in 95 countries, which speaks to its stability and scalability.

• Language & Framework: Pure PHP 7/8, following PSR‑4 autoloading and Composer for dependency management. The codebase is modular, with a plugin system that allows developers to drop in new handlers without touching core logic.
• Database: Relies on a relational database (MySQL/MariaDB or PostgreSQL) for subscriber data, campaign metadata, and analytics. The schema is normalized but heavily indexed to support high‑volume lookups.
• Queue & Delivery: Uses a custom message queue that can throttle and load‑balance across multiple SMTP or SES accounts. Delivery status is stored in a separate delivery table, enabling real‑time analytics and requeue logic.
• APIs & CLI: Exposes a REST API for CRUD operations on lists, subscribers, and campaigns. The CLI (phplist-cli) offers bulk import/export, campaign scheduling, and diagnostic commands.
• Containerization: Official Docker images are available (phplist/phplist) and can be orchestrated with Docker Compose or Kubernetes. The image layers are small, making CI/CD pipelines lightweight.

• Segmentation & Personalisation: Subscribers can be tagged with arbitrary attributes; templates support merge tags and conditional logic.
• Analytics: Real‑time tracking of opens, clicks, bounces, and spam complaints. Data is aggregated per campaign and exposed via API endpoints for custom dashboards.
• Bounce Management: Regex‑based policies allow developers to define granular handling rules (e.g., immediate suppression, delayed retry). All bounces are archived for audit.
• Multi‑Account Support: Seamlessly route messages through multiple SMTP or Amazon SES accounts, each with domain‑based throttling rules.
• Extensibility: A robust plugin architecture lets developers hook into events (e.g., beforeSend, afterBounce) and add new features such as GDPR compliance modules or third‑party analytics.

• Self‑Hosting: Requires a LAMP/LEMP stack with PHP ≥ 7.4, a supported database, and an SMTP server or SES credentials. The application is stateless aside from the database, making horizontal scaling trivial.
• Scalability: The queue can be distributed across multiple worker containers; each worker polls the database for pending messages. For very high throughput, a dedicated message broker (e.g., RabbitMQ) can be integrated via a plugin.
• High Availability: Database replication and load balancers are recommended for production. The web UI can be behind a reverse proxy (NGINX/Traefik) with HTTPS termination.

• Webhooks: External services can subscribe to events such as campaignSent or subscriberUnsubscribed. Payloads are JSON and can be consumed by microservices.
• Plugin System: Developers can create plugins that register callbacks, add new database tables, or expose custom API endpoints. The plugin manifest (plugin.json) declares dependencies and autoload paths.
• Custom Templates: Uses CKEditor for rich‑text editing; templates are stored in the database and can be programmatically generated or fetched from external CMS APIs.
• OAuth & SSO: Optional integrations with OAuth providers allow single‑sign‑on for admin panels, useful in enterprise deployments.

• Configuration: A single config.php file (or environment variables) controls database credentials, SMTP settings, and feature flags. The application ships with a config.sample.php that documents every option.
• Documentation: Comprehensive guides cover installation, API usage, plugin development, and advanced configuration. The community maintains a knowledge base on phplist.org.
• Community & Support: Active forums, GitHub issues, and a translation platform foster collaboration. The AGPL v3 license ensures that improvements remain open source.

1. Enterprise Newsletter Engine – Replace a SaaS provider with an on‑premises solution, retaining full control over data and compliance.
2. Custom Marketing Automation – Integrate with a CRM to trigger campaigns based on customer lifecycle events.
3. High‑Volume B2B Emailing – Leverage multi‑account routing and throttling to meet ISP limits while sending millions of transactional emails.
4. Data‑Driven Campaign Analysis – Build custom dashboards that consume the analytics API for real‑time reporting.

• Performance & Flexibility: The lightweight PHP core and database‑backed queue allow rapid scaling without a heavyweight message broker.
• Extensibility: The plugin architecture means developers can add or replace features without touching core code.
• Licensing: AGPL v3 guarantees that any derivative work remains open source, aligning with many organizations’ compliance policies.
• Community & Maturity: Over a decade of production use and an active contributor