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SMTP(8)                     System Manager's Manual                    SMTP(8)



NAME
       smtp, smtpd -  mail transport

SYNOPSIS
       upas/smtp [ -aAdfiops ] [ -b busted-mx ] ... [ -g gateway ] [ -h host ]
            [ -u user ] [ .domain ] destaddr sender rcpt-list

       upas/smtpd [ -adDfrg ] [ -c certfile ] [ -h mydom ] [ -k evilipaddr ] [
            -m mailer ] [ -n netdir ]

DESCRIPTION
       Smtp  sends the mail message from standard input to the users rcpt-list
       on the host at network address address using the Simple  Mail  Transfer
       Protocol.  The options are:

       -a     if  the server supports PLAIN or LOGIN authentication, authenti‐
              cate to the server using a password from factotum(4).  See  RFCs
              3207 and 2554.  This option implies -s.

       -A     autistic  server: don't wait for an SMTP greeting banner but im‐
              mediately send a command to provoke the server into responding.

       -b     ignore busted-mx when trying MX hosts.  May be repeated.

       -d     turn on debugging to standard error.

       -f     just filter the converted message to standard output rather than
              sending it.

       -g     makes  gateway  the  system to pass the message to if smtp can't
              find an address nor MX entry for the destination system.

       -h     use host as the local system name; it may be fully-qualified  or
              not.   If  not  specified,  it  will  default to the contents of
              /dev/sysname.

       -i     under -a, authenticate even if we can't start TLS.

       -o     under -s, use TLS even if we don't know the remote system.

       -p     ping: just verify that the users  named  in  the  rcpt-list  are
              valid users at destaddr; don't send any mail.

       -s     if  the  server  supports the ESMTP extension to use TLS encryp‐
              tion, turn it on for this session.  See RFC3207 for details.

       -u     specify a user name to be used in authentication.   The  default
              name is the current login id.

       Finally  if .domain is given, it is appended to the end of any unquali‐
       fied system names in the envelope or header.

       Smtpd receives a message  using  the  Simple  Mail  Transfer  Protocol.
       Standard  input and output are the protocol connection.  SMTP authenti‐
       cation by login and cram-md5 protocols is supported; authenticated con‐
       nections are permitted to relay.

       The options are:

       -a     requires that all clients authenticate to be able to send mail.

       -c     specifies  a  certificate  to use for TLS.  Without this option,
              the capability to start TLS will not be advertised.

       -d     turns on debugging output, with each connection's  output  going
              to a uniquely-named file in /sys/log/smtpdb.

       -D     sleeps for 15 seconds usually at the start of the SMTP dialogue;
              this deters some spammers.  Connections from  Class  A  networks
              frequented by spammers will incur a longer delay.

       -f     prevents  relaying from non-trusted networks.  It also tags mes‐
              sages from non-trusted sites when they deliver mail from an  ad‐
              dress in a domain we believe we represent.

       -g     turns on grey/white list processing.  All mail is rejected (with
              a  retry  code)  unless  the  sender's  IP  address  is  on  the
              whitelist, /mail/grey/whitelist, an append only file.  Addresses
              can be added to the whitelist by  the  administrator.   However,
              the  usual  way  for  addresses  to be added is by smtpd itself.
              Whenever a message is received and the sender's address isn't on
              the  whitelist,  smtpd  first looks for the file /mail/grey/tmp‐
              /local/remote/recipient, where local and remote are IP addresses
              of the local and remote systems, respectively.  If it exists and
              was created more than a few minutes go, the  remote  address  is
              added  to  the  whitelist.   If not, the file is created and the
              mail is rejected with a `try again' code.   The  expectation  is
              that  spammers  will  not  retry for more than a few minutes and
              that others will.

       -h     specifies the receiving domain.  If this flag is not  specified,
              the receiving domain is inferred from the host name.

       -k     causes  connections from the host at the IP address, evilipaddr,
              to be dropped at program startup.   Multiple  addresses  can  be
              specified  with  several -k options.  This option should be used
              carefully; it is intended to lessen the  effects  of  denial  of
              service  attacks  or  broken  mailers which continually connect.
              The connections are not logged and the remote system is not  no‐
              tified via the protocol.

       -m     set  the  mailer  to which smtpd passes a received message.  The
              default is /bin/upas/send.

       -n     specifies the name of the network directory assigned to the  in‐
              coming  connection.   This  is used to determine the peer IP ad‐
              dress.  If this flag is not specified, the peer address  is  de‐
              termined using standard input.

       -p     permits  clients  to authenticate using protocols which transfer
              the password in the clear, e.g.   login  protocol.  This  should
              only  be  used  if the connection has previously encrypted using
              e.g.  tlssrv(8).

       -r     turns on forward DNS validation of non-trusted sender address.

       -s     causes copies of blocked messages to be saved in a sub-directory
              of /mail/queue.dump.

       Smtpd is normally run by a network listener such as listen(8).  Most of
       the command line options are more conveniently specified in  the  smtpd
       configuration file stored in /mail/lib/smtpd.conf.

SOURCE
       /sys/src/cmd/upas/smtp

SEE ALSO
       aliasmail(8),  faces(1), filter(1), mail(1), marshal(1), mlmgr(1), ned‐
       mail(1), qer(8), rewrite(6), send(8), tlssrv(8), upasfs(4)



                                                                       SMTP(8)