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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




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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.