This is a working document. vSMTP v1.1.x is required.

Welcome to vBook, the vSMTP reference guide. It serves as vSMTP's primary documentation and tutorial resource.

Be aware that issues found in this documentation may have been fixed in the vSMTP repository already, as vBook is only updated for major releases of vSMTP.

What is vSMTP ?

vSMTP is a next-gen Mail Transfer Agent (MTA) developed by viridIT teams. You can follow viridIT on GitHub and

Why develop a new MTA ?

Whereas optimizing allocated resources is becoming a growing challenge, computer attacks remain a constant issue. Over 300 billion emails are sent and received in the world every day. Billions of attachments are processed, analyzed and delivered, contributing to the increase in greenhouse gas emissions. To meet this challenge, viridIT is developing a new technology of email gateways, also called vSMTP.

Why vSMTP is your future SMTP server ?

Because it is secured, faster and greener.

  • It is developed in Rust, implying high performance and stability.
  • It is modular and highly customizable.
  • It includes a complete filtering system.
  • It is actively maintained and developed.


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 vSMTP licence for further information.

This book is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. For further details please refer to the LICENSE file.

Source Code

The source files from which this book is generated can be found on GitHub.


We'd love your help! Please see the CONTRIBUTING file to learn about the kinds of contributions we're looking for.