vSMTP is a server that does not use a traditional configuration language to configure itself: it uses .vsl files (vSMTP Scripting Language) that are scripts based on the Rhai programming language with additional functions and syntax on top of it.


SMTP filtering is performed by a rule engine, which uses .vsl scripts to filter any incoming connection, email, user, etc.

Its syntax is similar to a configuration format, but with programmatic capabilities. It is based on two filtering primitives: rules and actions.

Please refer to the dedicated chapter guide on vSL for further details.

Service configuration

The vsmtp.service file contains all the mandatory information to start the vSMTP service on Linux server using systemd as the system and service manager.