smtp(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | HISTORY | COLOPHON

SMTP(1)                  General Commands Manual                 SMTP(1)

NAME         top

       smtp — Simple Mail Transfer Protocol client

SYNOPSIS         top

       [-Chnv] [-a authfile] [-F from] [-H helo] [-s server] [-T params]
       [recipient ...]

DESCRIPTION         top

       The utility is a Simple Mail Transfer Protocol (SMTP) client
       which can be used to run an SMTP transaction against an SMTP
       server.

       By default, 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
       data.

       The options are as follows:

       -a authfile
               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.

       -F from
               Set the return-path (MAIL FROM) for the SMTP transaction.
               Default to the current username.

       -H helo
               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.

       -s server
               Specify the server to connect to and connection
               parameters.  The format is
               [proto:https://[user:pass@]]host[:port].  The following
               protocols are available:

               smtp        Normal SMTP session with opportunistic
                           STARTTLS.
               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:https://localhost:25”.

       -T params
               Set specific parameters for TLS sessions.  The params
               string is a comma or space separated list of options.
               The available options are:

               cafile=filename
                       Use filename as root certificates file instead of
                       the system default.

               ciphers=value
                       Specify the allowed ciphers.  Refer to
                       tls_config_set_ciphers(3) for value.

               nosni   Disable Server Name Indication (SNI).

               noverify
                       Do not require server certificate to be valid.

               protocols=value
                       Specify the protocols to use.  Refer to
                       tls_config_parse_protocols(3) for value.

               servername=value
                       Use value for Server Name Indication (SNI).
                       Defaults to the specified server hostname.

       -v      Be more verbose.  This option can be specified multiple
               times.

SEE ALSO         top

       smtpd(8)

HISTORY         top

       The program first appeared in OpenBSD 6.4.

COLOPHON         top

       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 2023-12-22.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2023-12-05.)  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
       [email protected]

GNU                           May 23, 2021                       SMTP(1)