SMTP & LMTP transparent forwarding

Module that implements transparent forwarding of messages over SMTP.

Use in pipeline configuration:

deliver_to smtp tcp://
# or
deliver_to smtp tcp:// {
  # Other settings, see below.

target.lmtp can be used instead of target.smtp to use LMTP protocol.

Endpoint addresses use format described in Configuration files syntax / Address definitions.

Configuration directives

target.smtp {
    debug no
    tls_client {
    attempt_starttls yes
    require_tls no
    auth off
    targets tcp://
    connect_timeout 5m
    command_timeout 5m
    submission_timeout 12m

Syntax: debug boolean
Default: global directive value

Enable verbose logging.

Syntax: tls_client { ... }
Default: not specified

Advanced TLS client configuration options. See TLS configuration / Client for details.

Syntax: attempt_starttls boolean
Default: yes (no for target.lmtp)

Attempt to use STARTTLS if it is supported by the remote server. If TLS handshake fails, connection will be retried without STARTTLS unless 'require_tls' is also specified.

Syntax: require_tls boolean
Default: no

Refuse to pass messages over plain-text connections.

auth off
plain username password
Default: off

Specify the way to authenticate to the remote server. Valid values:

No authentication.

Authenticate using specified username-password pair. Don't use this without enforced TLS ('require_tls').

Forward credentials specified by the client. Don't use this without enforced TLS ('require_tls').

Request "external" SASL authentication. This is usually used for authentication using TLS client certificates. See TLS configuration / Client for details.

Syntax: targets endpoints...
Default: not specified


List of remote server addresses to use. See Address definitions for syntax to use. Basically, it is 'tcp://ADDRESS:PORT' for plain SMTP and 'tls://ADDRESS:PORT' for SMTPS (aka SMTP with Implicit TLS).

Multiple addresses can be specified, they will be tried in order until connection to one succeeds (including TLS handshake if TLS is required).

Syntax: connect_timeout duration
Default: 5m

Same as for target.remote.

Syntax: command_timeout duration
Default: 5m

Same as for target.remote.

Syntax: submission_timeout duration
Default: 12m

Same as for target.remote.