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A self-hosted Email API, built in Rust

Simple, Secure, and Ready for Modern Developers

Access IMAP and SMTP through one unified REST and gRPCinterface. Self-hosted, event-driven, source code available — with full control and privacy.

Easily sync hundreds of email accounts with a single instance

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An adaptable email middleware for many industries, helping you cut down development time by months.

SaaS & CRM Solutions

Easily connect and manage users’ mailboxes to gain real-time insights into their communication flows.

Digital Agencies

Empower clients with bespoke email features such as personalized newsletter and campaign systems.

Email Hosting Services

Deliver custom webmail experiences tightly integrated with your hosting platform.

Small and Medium Enterprises

Automate support and information mailbox management, reducing manual workload and improving response times.

Email Deliverability Specialists

Automate warmup processes across multiple accounts to boost sender reputation and inbox placement.

AI & Machine Learning Teams

Aggregate user emails securely to fuel data-driven models and enhance intelligence.

Web Hosting Providers

Streamline management of specialized mailboxes like postmaster and abuse reports for compliance and monitoring.

Large Enterprises

Serve as a secure IMAP/SMTP gateway bridging legacy systems with modern OAuth-enabled services like Microsoft 365.

Outreach & Sales Automation

Scale personalized email campaigns with automated sending and reply handling for efficient prospect engagement.

Build reliable email systems with ease.

Powerful infrastructure for email-based apps.

Own your email infrastructure
Deploy RustMailer on your own servers or private cloud. No external dependencies, no third-party lock-in.
Full support for IMAP and SMTP
Send and receive emails reliably using standard protocols. Compatible with Gmail, Outlook, Apple Mail, and most email providers.
Flexible deployment
Cross-platform, Docker-friendly, and runs without external services — just a ~60MB Rust binary.
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Built-in webmail client

Lightweight webmail UI for viewing synced emails and testing template deliveries.

Visualize synced mailboxes
Browse folders and messages in real time to verify sync behavior and folder state.
Inspect headers and metadata
Debug emails with detailed views of headers, flags, MIME structure, and threading info.
Preview test emails instantly
Send test messages from templates or MTAs and view the rendered results immediately within the webmail interface.
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Robust APIs for seamless email integration

Powerful REST & gRPC APIs with rich docs and flexible data handling.

Easy-to-use REST API
Standard JSON payloads hide IMAP and provider quirks—no need to deal with encodings or protocol edge cases.
Comprehensive API docs
Interactive documentation with OpenAPI, Swagger, ReDoc, Explorer, and Scalar—everything you need to get started fast.
Multi-language gRPC support
Generate client code automatically in multiple languages with gRPC—no manual data modeling required.
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Flexible and reliable event delivery

Email events delivered via Webhook or NATS — new messages, flags, and more.

Multiple event delivery options
Deliver real-time email events via webhooks or NATS, giving you flexible integration choices.
Comprehensive event coverage
Receive event notifications for new emails, deletions, and flag changes — triggered by periodic mailbox checks.
Customizable event payloads
Tailor event content before delivery — filter, transform, or enrich data to suit your system’s needs.
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Advanced event control with VRL scripting

Leverage VRL to gain full control over email event data — from filtering to payload transformation.

Flexible event filtering
Use VRL to selectively deliver events based on account, folder, flags, or any field you define.
Powerful event transformation
Modify event payloads on the fly — rename fields, remove sensitive data, or reshape to match your schema.
Enrich events with custom logic
Add derived values, timestamps, tags, or lookup results using simple and expressive VRL scripts.
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Simplified OAuth2 integration

Connect Gmail, Outlook, and others without handling tokens or refresh logic.

OAuth2 provider support
Supports Gmail, Outlook, and other IMAP/SMTP providers using OAuth2. Configure your own client ID and secret.
Encrypted credential storage
Client secrets, access tokens, and refresh tokens are encrypted at rest to protect sensitive authentication data.
Automatic token refresh
RustMailer handles token expiration and refresh behind the scenes, so you don’t need to manage it manually.
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Powerful Email Sending

Built for flexibility and control

Template-driven email generation
Create personalized emails at scale using Handlebars templates, dynamic variables, and content from EML files or past messages.
Flexible sending via SMTP or MTA
Send through the original SMTP server or external MTAs — choose based on deliverability, speed, or policy.
Open & click tracking with webhooks
Monitor user interactions in real time. Get webhook notifications for opens and clicks to power automation and analytics.
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Comprehensive Metrics & Monitoring

Gain full insight with detailed, out-of-the-box Prometheus metrics across all system components.

Comprehensive Metrics & Monitoring
Built-in, fine-grained Prometheus metrics covering email sending, IMAP traffic, webhook dispatch, and system task performance — enabling deep visibility into every aspect of your email system.
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Frequently asked questions

If you have additional questions, feel free to reach out to us

Save months of email infrastructure work.
Start using RustMailer today.

RustMailer is a lightweight, self-contained email sync and sending engine that lets you launch faster and reduce maintenance overhead.