The smtp utility is a Simple Mail Transfer Protocol (SMTP) client
which can be used to run an SMTP transaction against an SMTP
By default, smtp reads the mail content from the standard input,
establishes an SMTP session, and runs an SMTP transaction for all
the specified recipients. The content is sent unaltered as mail
The options are as follows:
Perform a login before sending the message. The username
and password are read from authfile and need to be on the
first and second line respectively. This option requires a
TLS or STARTTLS server.
-C Do not require server certificate to be valid. This flag
is deprecated. Use “-T noverify” instead.
Set the return-path (MAIL FROM) for the SMTP transaction.
Default to the current username.
Define the hostname to advertise (HELO) when establishing
the SMTP session.
-h Display usage.
-n Do not actually execute a transaction, just try to
establish an SMTP session and quit. When this option is
given, no message is read from the standard input.
Specify the server to connect to and connection parameters.
The format is [proto://[user:pass@]]host[:port]. The
following protocols are available:
smtp Normal SMTP session with opportunistic
smtp+tls Normal SMTP session with mandatory STARTTLS.
smtp+notls Plain text SMTP session without TLS.
lmtp LMTP session with opportunistic STARTTLS.
lmtp+tls LMTP session with mandatory STARTTLS.
lmtp+notls Plain text LMTP session without TLS.
smtps SMTP session with forced TLS on connection.
Defaults to “smtp://localhost:25”.
Set specific parameters for TLS sessions. The params
string is a comma or space separated list of options. The
available options are:
Use filename as root certificates file instead of
the system default.
Specify the allowed ciphers. Refer to
tls_config_set_ciphers(3) for value.
nosni Disable Server Name Indication (SNI).
Do not require server certificate to be valid.
Specify the protocols to use. Refer to
tls_config_parse_protocols(3) for value.
Use value for Server Name Indication (SNI).
Defaults to the specified server hostname.
-v Be more verbose. This option can be specified multiple
This page is part of the OpenSMTPD (a FREE implementation of the
server-side SMTP protocol) project. Information about the project
can be found at https://www.opensmtpd.org/. If you have a bug
report for this manual page, see
⟨https://github.com/OpenSMTPD/OpenSMTPD/issues⟩. This page was
obtained from the project's upstream Git repository
⟨https://github.com/OpenSMTPD/OpenSMTPD.git⟩ on 2023-06-23. (At
that time, the date of the most recent commit that was found in the
repository was 2023-06-23.) If you discover any rendering problems
in this HTML version of the page, or you believe there is a better
or more up-to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not part
of the original manual page), send a mail to firstname.lastname@example.org
BSD May 23, 2021 BSD