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https://github.com/stalwartlabs/smtp-server

Stalwart SMTP Server
https://github.com/stalwartlabs/smtp-server

arc dane dkim dmarc mta-sta sieve smtp spf

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Stalwart SMTP Server

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    Stalwart SMTP Server





  Secure & Modern SMTP Server 🛡️






  

    continuous integration

  

  

    License: AGPL v3

  

  

    Documentation

  

  


  

    Mastodon

  

  

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**Stalwart SMTP** is a modern SMTP server developed in Rust with a focus on security, speed, and extensive configurability. 

It features built-in DMARC, DKIM, SPF and ARC support for message authentication, strong transport security through DANE, MTA-STS and SMTP TLS reporting, and offers great flexibility and customization thanks to its dynamic configuration rules and native support for Sieve scripts.



Key features:



- Sender and Message Authentication:

  - Domain-based Message Authentication, Reporting, and Conformance (**DMARC**) verification and failure/aggregate reporting.

  - DomainKeys Identified Mail (**DKIM**) verification, signing and failure reporting.

  - Sender Policy Framework (**SPF**) policy evaluation and failure reporting.

  - Authenticated Received Chain (**ARC**) verification and sealing.

  - Reverse IP (**iprev**) validation.

- Strong Transport Security:

  - DNS-Based Authentication of Named Entities (**DANE**) Transport Layer Security.

  - SMTP MTA Strict Transport Security (**MTA-STS**).

  - SMTP TLS Reporting (**TLSRPT**) delivery and analysis.

- Inbound Filtering and Throttling:

  - Sieve scripting language with support for all [registered extensions](https://www.iana.org/assignments/sieve-extensions/sieve-extensions.xhtml).

  - **Milter** support for integration with external content filtering systems such as SpamAssassin and ClamAV.

  - Address rewriting.

  - Filtering, modification and removal of message parts or headers.

  - Inbound concurrency & rate limiting.

- **Spam and Phishing** filter:

  - Comprehensive set of filtering **rules** on par with popular solutions.

  - Statistical **spam classifier** with automatic training capabilities.

  - DNS Blocklists (**DNSBLs**) checking of IP addresses, domains, and hashes.

  - Collaborative digest-based spam filtering with **Pyzor**.

  - **Phishing** protection against homographic URL attacks, sender spoofing and other techniques.

  - Trusted **reply** tracking to recognize and prioritize genuine e-mail replies.

  - Sender **reputation** monitoring by IP address, ASN, domain and email address.

  - **Greylisting** to temporarily defer unknown senders.

  - **Spam traps** to set up decoy email addresses that catch and analyze spam.

- Flexible Queues:

  - Distributed and fault-tolerant queues.

  - Unlimited virtual queues with custom routing rules.

  - Delayed delivery with `FUTURERELEASE` and `DELIVERBY` extensions support.

  - Priority delivery with `MT-PRIORITY` extension support.

  - Outbound throttling & Disk quotas.

- Logging and Reporting:

  - Detailed logging of SMTP transactions and events, including delivery attempts, errors, and policy violations.

  - Integration with **OpenTelemetry** to enable monitoring, tracing, and performance analysis of SMTP server operations.

  - Automatic analysis of incoming DMARC/TLS aggregate reports, DMARC/DKIM/SPF authentication failure reports as well as abuse reports.

- And more:

  - SASL authentication.

  - Redis, LDAP, PostgreSQL, MySQL, MSSQL and SQLite support.

  - Email aliases, mailing lists, subaddressing and catch-all addresses support.

  - Granular configuration rules.

  - REST API for management.

  - Memory safe (thanks to Rust).



## Get Started



Install Stalwart SMTP Server on your server by following the instructions for your platform:



- [Linux / MacOS](https://stalw.art/docs/install/linux)

- [Windows](https://stalw.art/docs/install/windows)

- [Docker](https://stalw.art/docs/install/docker)



All documentation is available at [stalw.art/docs/get-started](https://stalw.art/docs/get-started).



> **Note**

> If you need a more comprehensive solution that includes IMAP and JMAP servers, you should consider installing the [Stalwart Mail Server](https://github.com/stalwartlabs/mail-server) instead.



## Support



If you are having problems running Stalwart SMTP, you found a bug or just have a question,

do not hesitate to reach us on [Github Discussions](https://github.com/stalwartlabs/smtp-server/discussions),

[Reddit](https://www.reddit.com/r/stalwartlabs) or [Discord](https://discord.gg/gNCVEEkWyX).

Additionally you may become a sponsor to obtain priority support from Stalwart Labs Ltd.



## Funding



Part of the development of this project was funded through the [NGI0 Entrust Fund](https://nlnet.nl/entrust), a fund established by [NLnet](https://nlnet.nl/) with financial support from the European Commission's [Next Generation Internet](https://ngi.eu/) programme, under the aegis of DG Communications Networks, Content and Technology under grant agreement No 101069594.



If you find the project useful you can help by [becoming a sponsor](https://liberapay.com/stalwartlabs). Thank you!



## License



Licensed under the terms of the [GNU Affero General Public License](https://www.gnu.org/licenses/agpl-3.0.en.html) as published by

the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

See [LICENSE](LICENSE) for more details.



You can be released from the requirements of the AGPLv3 license by purchasing

a commercial license. Please contact [email protected] for more details.

  

## Copyright



Copyright (C) 2020-2023, Stalwart Labs Ltd.