42 releases (18 stable)

2.2.1 Mar 31, 2023
2.1.1 Feb 10, 2023
1.4.0-rc.16 Jan 9, 2023
1.4.0-rc.7 Dec 19, 2022
1.1.3 Jul 12, 2022

#334 in Data structures

Download history 1/week @ 2023-12-24 9/week @ 2024-02-18 22/week @ 2024-02-25 12/week @ 2024-03-03 14/week @ 2024-03-10 17/week @ 2024-03-17 25/week @ 2024-03-24 551/week @ 2024-03-31

611 downloads per month
Used in 6 crates (5 directly)



⚠️ Breaking changes for vSMTP 2.1.1 to 2.2

Please take note that some breaking API changes in vsl have been introduced between versions 2.1.1 and 2.2 of vSMTP. Refer to the Changelogs for more details.

What is vSMTP ?

vSMTP is a next-gen Mail Transfer Agent (MTA), faster, safer and greener.

  • It is 100% built in Rust.
  • It is lightning fast.
  • It is modular and highly customizable.
  • It has a complete filtering system.
  • It is actively developed and maintained.

Faster, Safer, Greener

While optimizing IT resources becomes an increasing challenge, computer attacks remain a constant problem.

Every day, over 300 billion emails are sent and received in the world. Billions of attachments are processed, analyzed and delivered, contributing to the increase in greenhouse gas emissions.

To meet these challenges, viridIT is developing a new technology of email gateways, also called vSMTP.

Follow us on viridit.com


vSMTP enable you to create complex set of rules to filter your emails using vSMTP's scripting language (vsl) based on Rhai. You can:

  • inspect / modify the content of incoming emails.
  • forward and deliver emails locally or remotely.
  • connect to databases.
  • run commands.
  • quarantine emails.

and much more.

// -- /etc/vsmtp/service/database.vsl

// vSMTP can be extended with plugins.
import "plugins/vsmtp_plugin_mysql" as mysql;

// Here we declare a service.
// Let's connect to a mysql database.
export const database = mysql::connect(#{
    // the url to connect to the database.
    url: "mysql://localhost/?user=greylist-manager&password=my-password"",
    timeout: "30s",
    connections: 4,
// -- /etc/vsmtp/filter.vsl
// Here we declare our rules for filtering.

import "service/database" as db;

  // hook on the 'mail from' stage. (when the server receives the `MAIL FROM:` command)
  mail: [
    rule "greylist" || {
      let sender = ctx::mail_from();

      // is the user in our greylist ?
      // (don't forget to sanitize your inputs to prevent SQL injection)
      if db::greylist.query(`SELECT * FROM greylist.sender WHERE address = '${sender}';`).is_empty() {
        // it does not, we add the address to the database, then deny the email.
            INSERT INTO greylist.sender (user, domain, address)
            values ("${sender.local_part}", "${sender.domain}", "${sender}");
        // close the connection with a built in "451 - 4.7.1" error code.
      } else {
        // it is, we accept the email.

Check out the filtering chapter of the book and the vSL reference to get an overview of what you can do with vSL.


vSMTP can be extended via plugins. Here are some already available:

Check the Plugins chapter from the book for more details.


Comparison between Postfix 3.6.4 & vSMTP 1.0.1 performances, performed on a Ubuntu 22.04 LTS running with an AMD Ryzen 5 5600X 6-Core Processor.

Check out the "hold" benchmark readme to reproduce the above example, and the benchmarks readme to try other benchmarks.


In this repository, the "develop" branch is the branch that we work on every day to provide new features. If you want to check examples for the latest vSMTP versions, switch to the "main" branch, where our latest releases are delivered.

For documentation please consult our book, called vBook, the online reference and user guide for vSMTP. Documentation for the "develop" branch is also available in the book at https://vsmtp.rs/next.

To stay tuned, ask questions and get in-depth answers feel free to join our Discord server. You can also open GitHub discussions.


You can find more information about the project agenda in Milestones and the roadmap section.

You can check out updates in the Changelogs.


A guideline about contributing to vSMTP can be found in the contributing section.


We can offer a wide range of services, from design to physical implementation, provide maintenance and develop specific features and dedicated APIs to meet your business needs.

For any question related to commercial, licensing, etc. you can contact us on our website or send a message to contact@viridit.com.


The standard version of vSMTP is free and under an Open Source license.

It is provided as usual without any warranty. Please refer to the license for further information.


~1.5M SLoC