vSMTP is a Mail Transfer Agent (MTA) and a Mail Submission Agent (MSA).

It is not intended to be a Mail User Agent (MUA) nor a Mail Delivery Agent (MDA).

For outgoing mail, vSMTP can directly be addressed by your MUA using the SMTP protocol.

For incoming mails, vSMTP can deliver local mail to a client storage using mbox or maildir formats. To retrieve emails from your MUA it is necessary to install a MDA that can handle POP and/or IMAP protocols.

☞ | For Debian/Ubuntu server the most straightforward solution is to download and install courier-imap package and specify to the courier-imap MDA where are located the MailDir/ folders and use a MUA like Mozilla ThunderBird.


Take a look at the ROADMAP in vSMTP repository.

Follow the development of vsmtp, plannings and announcements for incoming features on the official discord server.

Available features


  • Listen and serve on multiple addresses.
  • Support for IPv4 and IPv6 format.
  • Built on high performance asynchronous connections.
  • Handle one or multiple emails per connections.
  • Compliancy with Internet Message Format and Simple Mail Transfer Protocol RFCs.
  • TLS 1.3 support.
  • Complete DNS configurations - thanks to Benjamin Fry’s Trust-DNS crate.
  • Support for high workload through built-in mechanisms.


vSMTP is modular and highly customizable. Adding or modifying subsystems is facilitated by the internal design of the software. An API is available allowing easy integration into existing security elements. Several native plug-ins are already available.

  • Mail exports in raw and json format.
  • Third-party softwares called by user-defined services.
  • Mods and addons support.
  • Applications logs.


vSMTP has a complete filtering system. In addition to the standard analysis of the SMTP envelope, vsmtp adds the possibility of interacting on the fly on the content of messages (MIME). It is possible to filter, modify, encrypt, etc. any part of an email. Users can generate complex routing and filtering scenarios through a simple and intuitive advanced scripting language.

  • Before and after queueing filtering.
  • vSMTP scripting language allowing administrators to define complex rules.
  • Interaction at each SMTP state (HELO/EHLO, CONNECT, MAIL, RCPT, DATA).


  • SMTP remote delivery - using a third-party software, Lettre.
  • Mbox and Maildir format for local delivering.
  • SMTP relaying and forwarding.

External services

vSMTP supports SMTP delegation, command calls and file databases. Next versions will bring SQL and NoSQL databases and in-memory caches supports. Compliancy with Postfix SMTP access policy delegation and Unix/IP socket calls are planned for Q3/2022.

Email authentication mechanisms

  • Message submission RFCs.
  • Null MX RFC.
  • SPF support.
  • DKIM signer and verifier.
  • DMARC is planned for the next minor release.
  • DANE protocol is planned for future release.
  • ARC and BIMI experimental and future Internet standards are currently not supported.