Best Self Hosted Alternatives to Mailgun

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.

Mautic is a self-hosted marketing automation platform for creating, delivering, and measuring multi-channel campaigns across email and other customer touchpoints. It combines contact management, segmentation, and campaign orchestration to help teams run personalized journeys and track engagement over time.

Key Features

• Visual Campaign Builder to design automated customer journeys with decisions/actions
• Email marketing with template/asset management, scheduling, and performance reporting
• Segmentation and dynamic contact lists based on behavior and attributes
• Forms and Landing Pages for lead capture (including progressive profiling)
• Lead scoring and lead nurturing tools to qualify and route contacts
• Multi-channel messaging support via plugins/integrations (e.g., SMS, webhooks)
• REST API and webhooks for integrations with CRMs, e-commerce, and data pipelines
• Role-based access control and multi-user administration

Use Cases

• Automate onboarding/drip sequences for product trials and SaaS signups
• Run segmented newsletters and targeted lifecycle campaigns based on behavior
• Capture leads via forms/landing pages and sync them to a CRM for sales follow-up

Limitations and Considerations

• Some channels/connectors are provided via plugins and may require additional configuration/maintenance
• Deliverability depends heavily on correct SMTP setup, DNS (SPF/DKIM/DMARC), and reputation management

Mautic is well-suited for teams that need full control over marketing automation infrastructure while keeping strong campaign capabilities. Its combination of segmentation, journey automation, and integration options makes it a flexible alternative to many hosted marketing automation suites.

Mailu is a full mail server stack distributed as a set of Docker containers, providing SMTP and IMAP services plus webmail and administration. It aims to make running a secure, standards-compliant email server easier by bundling the common components and exposing a web UI for daily management.

Key Features

• Complete mail stack in containers: SMTP (Postfix), IMAP (Dovecot), and web front-end services
• Web administration interface to manage domains, users/mailboxes, aliases, and credentials
• Built-in anti-spam and content filtering using Rspamd (with milter integration)
• Optional antivirus scanning via ClamAV
• Email authentication support (e.g., DKIM signing via OpenDKIM; DMARC-related configuration documented)
• Webmail via Roundcube (optional) and support for additional services depending on deployment profile
• Multiple deployment options and profiles (e.g., docker-compose; behind reverse proxies such as Traefik)

Use Cases

• Self-managed email hosting for a personal domain (mailboxes and aliases)
• Small organization mail service with web-based administration and spam/virus filtering
• Lab/home server mail stack for learning and testing SMTP/IMAP, DKIM, and anti-spam configuration

Limitations and Considerations

• Operating a deliverable email service requires correct DNS configuration (MX, SPF, DKIM, DMARC) and ongoing reputation/anti-abuse management
• Some features depend on optional containers/services (e.g., webmail, antivirus), increasing resource usage and operational complexity

Mailu provides an integrated, container-first approach to email hosting that combines the core MTAs/IMAP server with a management UI and anti-spam/AV components. It is a practical choice when you want a cohesive, well-known mail stack with minimal manual wiring between services.