Logging

The logging system is backed by tokio tracing and piped to multiple ‘subscriber’ :

• Logging
  • Backend logs
  • Application logs
  • Syslogd
  • Journald

Backend logs

Backend logs concerns the vSMTP internals output.

The default output directory is /var/log/vsmtp/vsmtp.log.

Log levels can be configured by “modules”, representing part of the server, using the env_logger syntax (see docs.rs). The vsmtp_rule_engine module enables logs for the rule engine, the vsmtp_mail_parser module for the mime parser, etc.

The vsmtp.toml file is used to configure server logs:

[server.logs]
# You can change the location of the server logs.
filepath = "./tmp/system/vsmtp.log"

level = [
    # set global logging level to "info" for all the modules.
    "info",

    # set the logging level per module.
    "vsmtp_server::receiver=info",
    "vsmtp_rule_engine=warn",
    "vsmtp_delivery=error",
]

Application logs

Application logs are defined using the log(level, message) function in the vSL rules.

The default output location (/var/log/vsmtp/app.log) can be modified in the vsmtp.toml file :

[app.logs]
# You can change the location of the application logs.
filepath = "./tmp/system/app.log"

Syslogd

vSMTP send logs to the syslog daemon using the mail facility :

# if the table is missing, system's log are skipped
[server.logs.system]
# write only the message of a specific level and more
level = "info"
backend = "syslogd"
# format used by the logger see https://www.rfc-editor.org/rfc/rfc3164 and https://www.rfc-editor.org/rfc/rfc5424
format = "3164"

socket = { type = "unix", path = "/dev/log" }
# or
socket = { type = "tcp", server = "127.0.0.1:601" }
# or
socket = { type = "udp", server = "127.0.0.1:514", local = "127.0.0.1:0" }
# note: address can be ipv4 / ipv6

Journald

vSMTP send logs to the journald daemon :

# if the table is missing, system's log are skipped
[server.logs.system]
# write only the message of a specific level and more
level = "info"
backend = "journald"