Next-gen MTA. Secured, Faster and Greener

3 stable releases

Uses new Rust 2021

1.1.0 Jun 20, 2022
1.0.2 Jun 7, 2022
1.0.0 May 16, 2022

#21 in Configuration

Download history 31/week @ 2022-05-16 48/week @ 2022-05-23 12/week @ 2022-05-30 35/week @ 2022-06-06 9/week @ 2022-06-13 49/week @ 2022-06-20

106 downloads per month
Used in 2 crates (via vsmtp-server)


12K SLoC

What is vSMTP ?

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

  • It is 100% built in Rust.
  • It is lighting 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 the vsl programming language 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.

// -- database.vsl
// here we declare our services.
// connect to a database with the csv format.
service greylist db:csv = #{
  connector: "/db/greylist.csv",
  access: "O_RDWR",
  refresh: "always",
  delimiter: ',',
// -- main.vsl
// here we declare our rules for filtering.

import "database" as db;

  // hook on the 'mail from' stage.
  mail: [
    // you can decide to accept or deny an email with a "rule".
    rule "greylist" || {

      let sender = ctx().mail_from;

      // is the user in our greylist ?
      if db::greylist.get(sender).len() != 0 {
        // it is, we accept the email.
      } else {
        // it does not, we add the address to the database, then deny the email.
        db::greylist.set([ sender ]);


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 benchmarks readme to get reproducible examples.


For documentation please consult the vBook, the online reference and user guide for vSMTP.

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


vSMTP is currently under development.

The next releases "1.2.x" will focus on SQL databases support, DKIM & DMARK. You can find more information about the project agenda in the roadmap.

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


For any question related to commercial, licensing, etc. you can contact us on our website.


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.


~769K SLoC