Best Self Hosted Alternatives to Postmark

Postal is an open-source mail delivery platform designed for sending transactional email from applications using your own infrastructure. It provides SMTP and an HTTP API, plus a web interface to manage organizations, servers, credentials, and to inspect message activity.

Key Features

• SMTP server for application email delivery with per-server credentials
• HTTP API for sending messages programmatically
• Web-based administrative UI for managing organizations/servers/users
• Message tracking/logs for sent mail, including delivery attempts and status
• Support for multiple “mail servers” and separation by organization/team
• Domain and routing configuration tooling oriented around transactional mail

Use Cases

• Replace third-party transactional email providers for product emails (signups, password resets, receipts)
• Centralize outbound mail delivery for multiple apps/services with separate credentials
• Operate an internal email relay with auditing/visibility into outbound messages

Limitations and Considerations

• Primarily focused on outbound/transactional delivery (not a groupware mailbox server)
• Requires correct DNS and deliverability configuration (SPF/DKIM/DMARC) and ongoing reputation management

Postal is suitable when you need control over outbound email delivery, want an API/SMTP interface for applications, and need a UI for operational visibility. It provides the core primitives for delivering and tracking mail without relying on hosted email-sending services.

Mail-in-a-Box is an opinionated all-in-one setup that turns a fresh Ubuntu server into a working email system for your domain(s). It bundles the core components needed to run mail reliably (sending/receiving, security, spam filtering, DNS, and webmail) and manages them through a simple web-based control panel.

Key Features

• One-command installation on a supported Ubuntu release (designed for a clean VPS)
• Admin control panel for users, aliases, domains, and service status
• Integrated webmail (Roundcube) plus IMAP/SMTP support for desktop/mobile clients
• Built-in DNS server/management to publish required records (MX, SPF, DKIM, DMARC, etc.)
• Automatic TLS certificates via Let’s Encrypt (ACME) for HTTPS/IMAPS/SMTPS
• Spam filtering and basic anti-abuse tooling (e.g., greylisting/antispam integration)
• Contact/calendar sync support via CardDAV/CalDAV (via bundled groupware components)

Use Cases

• Host email for a personal domain or small organization without outsourcing to a provider
• Replace hosted email suites for basic mail + webmail needs
• Provide mailboxes and aliases for multiple domains from a single server

Limitations and Considerations

• Opinionated stack and OS support: intended for a specific Ubuntu version on a clean server
• Advanced enterprise features (large-scale clustering, complex compliance tooling) are not the primary focus

Mail-in-a-Box is a practical choice when you want a complete, integrated mail setup with sane defaults and a straightforward admin experience. It emphasizes simplicity and a cohesive configuration over modular, pick-and-choose assembly.

Stalwart is a modern, self-contained email server designed to run a complete mail stack (sending, receiving, and mailbox access) with strong security controls and built-in filtering. It aims to simplify operating mail infrastructure by bundling protocols, authentication, policy, and anti-abuse features into a single service with an administrative UI.

Key Features:

• Supports core mail access and transport protocols including SMTP and IMAP, with JMAP support for modern clients
• Built-in anti-spam and policy enforcement with rules, reputation controls, and content filtering
• Email authentication features such as DKIM signing and DMARC/SPF evaluation to improve deliverability and prevent spoofing
• Flexible message routing, domain/user management, and multi-domain support for organizations
• Web-based administration interface for configuration and operational management
• TLS support and modern security defaults oriented toward safer deployments

Use Cases:

• Run a private email service for a personal domain or small organization
• Replace a hosted mailbox provider while keeping control of deliverability and anti-spam
• Operate multi-tenant email for multiple domains with centralized management

Stalwart provides a cohesive, security-focused approach to running email by combining protocols, filtering, and administration in one package. It is well-suited for operators who want a modern mail stack with fewer external components to integrate and maintain.

Keila is an open-source, self-hosted email newsletter and marketing email platform. It helps teams and creators build mailing lists, design email campaigns, schedule/automate sending, and track engagement.

Key Features

• Audience management with lists and subscriber attributes (including imports)
• Campaign editor with reusable templates and drag-and-drop style blocks (email builder)
• Segmentation to target subsets of subscribers based on attributes/filters
• Automations for triggered or scheduled sends (e.g., onboarding/drip sequences)
• Email delivery via SMTP and support for transactional sending flows
• Analytics for campaign performance (e.g., opens/clicks) and delivery status
• Multi-user/team oriented workflows (accounts/projects) suitable for organizations

Use Cases

• Publish recurring newsletters for communities, products, or internal updates
• Run lifecycle email sequences (welcome/onboarding/drip campaigns)
• Replace hosted email marketing tools where data/control must remain in-house

Limitations and Considerations

• Email analytics accuracy depends on client-side tracking behavior (e.g., image blocking/privacy features)
• Deliverability depends heavily on correct DNS (SPF/DKIM/DMARC) and SMTP provider configuration

Keila is a practical alternative to hosted newsletter tools for organizations that need list management, campaign creation, and automation in one place. It focuses on the core newsletter workflow—create, segment, send, and measure—while keeping operations under your control.