NAME

       msmtpd - A minimal SMTP server

SYNOPSIS

       msmtpd [option...]

DESCRIPTION

       Msmtpd  is  a minimal SMTP server that pipes mails to msmtp (or some other program) for delivery.  It can
       be used with system services that expect an SMTP server on the local host, or it can be used by end users
       as a way to handle outgoing mail via msmtp with mail clients that insist on  using  SMTP.   The  EXAMPLES
       section below contains examples for both use cases.
       Msmtpd listens on 127.0.0.1 port 25 by default, but can also run without its own network sockets in inetd
       mode, where it handles a single SMTP session on standard input / output.
       In the string that defines the command that msmtpd pipes each mail to, the first occurrence of %F will be
       replaced  with  the  envelope  from address.  Furthermore, all recipients of the mail will be appended as
       arguments. The command must not write to standard output, as that would mess up the SMTP session.
       If the command that the mail is piped to reports an error, this is  typically  reported  as  a  permanent
       failure  by  msmtpd  (SMTP server return code 554). The command can optionally signal temporary errors by
       using return codes defined in sysexits.h, e.g. 75  for  EX_TEMPFAIL.  These  will  then  be  reported  as
       temporary  failures  by  msmtpd  (SMTP  server  return code 451), which means the client should try again
       later.
       To prevent abuse, msmtpd  will  allow  only  a  limited  number  of  concurrent  SMTP  sessions,  and  if
       authentication  is  active  and  an authentication failure occurrs, future authentication requests in any
       SMTP session will (for a limited duration) only be answered after a small delay.

OPTIONS

       --version
              Print version information

       --help Print help

       --inetd
              Start single SMTP session on stdin/stdout

       --interface=ip
              Listen on the given IPv6 or IPv4 address instead of 127.0.0.1

       --port=number
              Listen on the given port number instead of 25

       --log=none|syslog|filename
              Set logging: none (default), syslog, or logging to the given file.

       --command=cmd
              Pipe mails to cmd instead of msmtp.  Make sure to end this command with  --  to  separate  options
              from arguments.

       --auth=user[,passwordeval]
              Require  authentication  with  this  user  name.  The  password  will  be retrieved from the given
              passwordeval command (this works just like passwordeval in msmtp) or, if none is given,  from  the
              key ring or, if that fails, from a prompt.

EXAMPLES

       Using msmtpd as a system service
       Only  use  a  local interface to listen on. Run msmtpd with correct user rights and permissions (e.g. use
       CAP_NET_BIND_SERVICE to bind to port 25 instead of running as root, or use  systemd  with  inetd  service
       capabilities).  Be  aware that the pipe command will be run as the same user that msmtpd runs as.  Enable
       logging to syslog with --log=syslog.
       Example for managing msmtpd with start-stop-daemon:
       # start msmtpd
       start-stop-daemon --start --pidfile /var/run/msmtpd.pid --make-pidfile --chuid msmtpd --background --exec
       /usr/local/bin/msmtpd -- --command '/usr/local/bin/msmtp -f %F --'
       # stop msmtpd
       start-stop-daemon --stop  --pidfile /var/run/msmtpd.pid --remove-pidfile --quiet --signal TERM
       Using msmtpd to handle outgoing mail for an SMTP-based mail client
       Some mail clients cannot send outgoing mail with a program like msmtp and instead insist on using an SMTP
       server. You can configure msmtpd to be that SMTP server and hand your outgoing mail over to msmtp.
       (Similarly, some mail clients cannot get incoming mail from a local mailbox and insist on using a POP3 or
       IMAP server. You can configure mpopd to be that POP3 server and serve incoming mail from a local mailbox.
       See the relevant section in the mpop manual.)
       For this purpose, msmtpd should listen on an unprivileged port, e.g. 2500.   Furthermore,  msmtpd  should
       require  authentication  because otherwise anyone connecting to it can send mail using your account, even
       if it's just other users or processes on your local machine.
       Let's use the user name msmtpd-user for this purpose. You have two options to manage the password:

              Store the password in your key ring, e.g. with secret-tool  store  --label=msmtpd  host  localhost
              service smtp user msmtpd-user.  In this case, use the msmtpd option --auth=msmtpd-user.

              Store  the  password  in  an  encrypted  file and use the passwordeval mechanism. Example for gpg:
              msmtpd ... --auth=msmtpd-user,'gpg -q -d ~/.msmtpd-password.gpg'

       The  complete  command   then   is   (using   the   keyring):   msmtpd   --port=2500   --auth=msmtpd-user
       --command='/path/to/your/msmtp -f %F --'
       The  mail  client  software  must  then be configured to use localhost at port 2500 for outgoing mail via
       SMTP, and to use authentication with user msmtpd-user and the password you chose. The  mail  client  will
       probably  complain  that  the SMTP server does not support TLS, but in this special case that is ok since
       all communication between your mail client and msmtpd will stay on the local machine.
       This setup also works with multiple mail accounts. Msmtp will pick the correct one based on the envelope-
       from address given to it via -f %F. You do not need multiple instances of msmtpd for  this  purpose,  and
       therefore you need only one SMTP server in your mail client configuration.

SEE ALSO

       msmtp(1)

                                                     2021-09                                           MSMTPD(1)