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man pages section 8: System Administration Commands

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Updated: Wednesday, February 9, 2022

etrn (8)


etrn - start mail queue run


etrn [-b] [-v] server-host [client-hosts]


System Administration Commands                                         etrn(8)

       etrn - start mail queue run

       etrn [-b] [-v] server-host [client-hosts]

       SMTP's  ETRN command allows an SMTP client and server to interact, giv-
       ing the server an opportunity to start the processing of its queues for
       messages  to  go  to a given host. This is meant to be used in start-up
       conditions, as well as for mail nodes that have  transient  connections
       to their service providers.

       The  etrn  utility  initiates an SMTP session with the host server-host
       and sends one or more ETRN commands as follows: If no client-hosts  are
       specified,  etrn looks up every host name for which sendmail(8) accepts
       email and, for each name, sends an ETRN command with that name  as  the
       argument. If any client-hosts are specified, etrn uses each of these as
       arguments for successive ETRN commands.

       The following options are supported:

       -b    System boot special case. Make sure localhost is  accepting  SMTP
             connections before initiating the SMTP session with server-host.

             This option is useful because it prevents race conditions between
             sendmail(8) accepting connections and server-host  attempting  to
             deliver  queued mail. This check is performed automatically if no
             client-hosts are specified.

       -v    The normal mode of operation for etrn is to do all  of  its  work
             silently.  The  -v  option makes it verbose, which causes etrn to
             display its conversations with the remote SMTP server.

       No  environment  variables  are  used.  However,  at  system  start-up,
       svc:/network/smtp:sendmail  reads  /etc/default/sendmail. In this file,
       if the variable ETRN_HOSTS is  set,  svc:/network/smtp:sendmail  parses
       this  variable  and invokes etrn appropriately. ETRN_HOSTS should be of
       the form:

         "s1:c1.1,c1.2        s2:c2.1 s3:c3.1,c3.2,c3.3"

       That is, white-space separated groups of server:client where client can
       be  one  or  more  comma-separated names. The :client part is optional.
       server is the name of the server to prod; a mail queue run is requested
       for each client name. This is comparable to running:

         /usr/lib/sendmail -qR client

       on the host server.

       Example 1 Using etrn

       Inserting the line:

         ETRN_HOSTS="s1.domain.com:clnt.domain.com s2.domain.com:clnt.domain.com"

       in /etc/default/sendmail results in svc:/network/smtp:sendmail invoking
       etrn such that  ETRN  commands  are  sent  to  both  s1.domain.com  and
       s2.domain.com, with both having clnt.domain.com as the ETRN argument.

       The line:


       results  in two ETRN commands being sent to server.domain.com, one with
       the  argument  client1.domain.com,  the   other   with   the   argument

       The line:

         ETRN_HOSTS="server1.domain.com server2.domain.com"

       results in set of a ETRN commands being sent to both server1.domain.com
       and server2.domain.com; each set contains one  ETRN  command  for  each
       host  name  for which sendmail(8) accepts email, with that host name as
       the argument.

       /etc/mail/sendmail.cf    sendmail configuration file

       /etc/default/sendmail    Variables used by svc:/network/smtp:sendmail

       See attributes(7) for descriptions of the following attributes:

       |      ATTRIBUTE TYPE         |       ATTRIBUTE VALUE        |
       |Availability                 |service/network/smtp/sendmail |
       |Interface Stability          |Committed                     |

       attributes(7), sendmail(8)

       RFC 1985

       Not all SMTP servers support ETRN.

Solaris 11.4                      8 Mar 2016                           etrn(8)