man > SLOCAL(1mh)

SLOCAL(1mh)                                                                              SLOCAL(1mh)

NAME
       slocal - asynchronously filter and deliver new mail to nmh

SYNOPSIS


       /usr/lib/mh/slocal [-help] [-version] [-addr address] [-info data] [-sender sender] [-user
            username] [-mailbox mbox] [-file file] [-maildelivery deliveryfile] [-verbose | -nover‐
            bose] [-suppressdup | -nosuppressdup] [-debug]

DESCRIPTION
       slocal  is a program designed to allow you to have your inbound mail processed according to a
       complex set of selection criteria.  You do not normally invoke slocal yourself, rather slocal
       is invoked on your behalf by your system's Message Transfer Agent (such as sendmail) when the
       message arrives.

       The message selection criteria used by slocal is specified in the file “.maildelivery” in the
       user's home directory.  You can specify an alternate file with the -maildelivery file option.
       The syntax of this file is specified below.

       The message delivery address and message sender are  determined  from  the  Message  Transfer
       Agent  envelope  information, if possible.  Under sendmail, the sender will obtained from the
       UUCP “From:” line, if present.  The user may override these values with the -addr and -sender
       switches.

       The message is normally read from the standard input.  The -file switch sets the name of  the
       file  from  which  the message should be read, instead of reading stdin.  This is useful when
       debugging a “.maildelivery” file.

       The -user switch tells slocal the name of the user for whom it is delivering mail.   It  must
       exist on the local system.  The -mailbox switch tells slocal the name of the user's mail drop
       file.

       slocal  is  able  to  detect and suppress duplicate messages.  To enable this, use the option
       -suppressdup.  slocal will keep a database containing the Message-ID's of incoming  messages,
       in order to detect duplicates.  Depending on your configuration, this database will be in ei‐
       ther ndbm or Berkeley db format.

       The  -info switch may be used to pass an arbitrary argument to sub-processes which slocal may
       invoke on your behalf.

       The -verbose switch causes slocal to give information on stdout about its progress.  The -de‐
       bug switch produces more verbose debugging output on stderr.  These  flags  are  useful  when
       creating  and debugging your “.maildelivery” file, as they allow you to see the decisions and
       actions that slocal is taking, as well as check for syntax  errors  in  your  “.maildelivery”
       file.

   Message Transfer Agents
       Most  modern MTAs including sendmail, postfix, and exim support a .forward file for directing
       incoming mail.  You should include the line

                                   “| /usr/lib/mh/slocal -user username”

       in your .forward file in your home directory.  This will cause your MTA to invoke  slocal  on
       your behalf when a message arrives.

   The Maildelivery File
       The  “.maildelivery”  file controls how slocal filters and delivers incoming mail.  Each line
       of this file consists of five fields, separated by whitespace or comma.  Since  double-quotes
       are  honored,  these  characters may be included in a single argument by enclosing the entire
       argument in double-quotes.  A double-quote can be included by preceding it with a  backslash.
       Lines beginning with `#' and blank lines are ignored.

       The format of each line in the “.maildelivery” file is:

            header    pattern   action    result    string

       header:
            The  name of a header field (such as To, Cc,  or From) that is to be searched for a pat‐
            tern.  This is any field in the headers of the message that might be present.

            The following special fields are also defined:

            source    the out-of-band sender information

            addr      the address that was used to cause delivery to the recipient

            default   this matches only if the message hasn't been delivered yet

            *         this always matches

       pattern:
            The sequence of characters to match in the specified header field.  Matching is case-in‐
            sensitive, but does not use regular expressions.

       action:
            The action to take to deliver the message.  When  a  message  is  delivered,  a  “Deliv‐
            ery-Date: date”  header  is added which indicates the date and time that message was de‐
            livered.

            destroy
                This action always succeeds.

            file, mbox, or >
                Append the message to the file named by string.  The message is appended to the file
                in mbox (uucp) format.  This is the format used by most other mail clients (such  as
                mailx, elm).  If the message can be appended to the file, then this action succeeds.

            mmdf
                Identical to file, but always appends the message using the MMDF mailbox format.

            pipe or |
                Pipe  the  message  as  the standard input to the command named by string, using the
                Bourne shell sh to interpret the string.  Prior to giving the string to  the  shell,
                it is expanded with the following built-in variables:

                $(sender)     the out-of-band sender information

                $(address)    the address that was used to cause delivery to the recipient

                $(size)       the size of the message in bytes

                $(reply-to)   either the “Reply-To:” or “From:” field of the message

                $(info)       the out-of-band information specified

            qpipe or ^
                Similar  to  pipe, but executes the command directly, after built-in variable expan‐
                sion, without assistance from the shell.  This action can be used to  avoid  quoting
                special characters which your shell might interpret.

            folder or +
                Store the message in the nmh folder named by string by piping the message to the nmh
                program rcvstore.

       result:
            Indicates how the action should be performed:

            A   Perform  the  action.  If the action succeeds, then the message is considered deliv‐
                ered.

            R   Perform the action.  Regardless of the outcome of the action,  the  message  is  not
                considered delivered.

            ?   Perform  the  action only if the message has not been delivered.  If the action suc‐
                ceeds, then the message is considered delivered.

            N   Perform the action only if the message has not been delivered and the  previous  ac‐
                tion succeeded.  If this action succeeds, then the message is considered delivered.

            The  delivery  file  is  always read completely, so that several matches can be made and
            several actions can be taken.

   Security of Delivery Files
       In order to prevent security problems, the “.maildelivery” file must be owned either  by  the
       user  or  by root, and must be writable only by the owner.  If this is not the case, the file
       is not read.

       If the “.maildelivery” file cannot be found, or does not perform an action which delivers the
       message, then slocal will check for a global delivery file  at  /etc/nmh/maildelivery.   This
       file  is  read  according  to  the  same  rules.  This file must be owned by root and must be
       writable only by root.

       If a global delivery file cannot be found or does not perform an action  which  delivers  the
       message, then standard delivery to the user's mail drop is performed.

   Example Delivery File
       To summarize, here's an example delivery file:

       #
       # .maildelivery file for nmh's slocal
       #
       # Blank lines and lines beginning with a '#' are ignored
       #
       # FIELD   PATTERN   ACTION  RESULT  STRING
       #

       # File mail with foobar in the “To:” line into file foobar.log
       To        foobar    file    A       foobar.log

       # Pipe messages from coleman to the program message-archive
       From      coleman   pipe    A       /bin/message-archive

       # Anything to the “nmh-workers” mailing list is put in
       # its own folder, if not filed already
       To        nmh-workers  folder ?     nmh-workers

       # Anything with Unix in the subject is put into
       # the file unix-mail
       Subject   unix      file    A       unix-mail

       # I don't want to read mail from Steve, so destroy it
       From      steve     destroy A       -

       # Put anything not matched yet into mailbox
       default   -        file    ?       mailbox

       # always run rcvtty
       *         -        pipe    R       /usr/lib/mh/rcvtty

   Sub-process environment
       When a process is invoked, its environment is: the user/group-ids are set to recipient's ids;
       the  working  directory is the recipient's home directory; the umask is 0077; the process has
       no /dev/tty; the standard input is set to the message; the  standard  output  and  diagnostic
       output are set to /dev/null; all other file-descriptors are closed; the environment variables
       $USER, $HOME, $SHELL are set appropriately, and no other environment variables exist.

       The  process  is  given  a  certain  amount of time to execute.  If the process does not exit
       within this limit, the process will be terminated with extreme prejudice.  The amount of time
       is calculated as ((size / 60) + 300) seconds, where size is the number of bytes in  the  mes‐
       sage (with 30 minutes the maximum time allowed).

       The  exit  status  of  the process is consulted in determining the success of the action.  An
       exit status of zero means that the action succeeded.  Any other exit status (or abnormal ter‐
       mination) means that the action failed.

       In order to avoid any  time  limitations,  you  might  implement  a  process  that  began  by
       fork()-ing.   The  parent would return the appropriate value immediately, and the child could
       continue on, doing whatever it wanted for as long as it wanted.  This  approach  is  somewhat
       risky if the parent is going to return an exit status of zero.  If the parent is going to re‐
       turn  a  non-zero exit status, then this approach can lead to quicker delivery into your mail
       drop.

FILES
       /etc/nmh/mts.conf          nmh mts configuration file
       $HOME/.maildelivery        The file controlling local delivery
       /etc/nmh/maildelivery      Rather than the standard file
       /var/mail/$USER            The default mail drop

SEE ALSO
       rcvdist(1), rcvpack(1), rcvstore(1), rcvtty(1), mh-format(5)

DEFAULTS
       `-noverbose'
       `-nosuppressdup'
       `-maildelivery' defaults to $HOME/.maildelivery
       `-mailbox' defaults to /var/mail/$USER
       `-file' defaults to stdin
       `-addr' defaults to the current user
       `-user' defaults to the current user

       -addr and -user will be set the the user part of the Local-Mailbox profile entry, if set.

CONTEXT
       None

HISTORY
       slocal was originally designed to be backward-compatible with the maildelivery facility  pro‐
       vided by MMDF-II.  Thus, the “.maildelivery” file syntax is somewhat limited.  But slocal has
       been modified and extended, so that is it no longer compatible with MMDF-II.

       In  addition  to  an exit status of zero, the MMDF values RP_MOK (32) and RP_OK (9) mean that
       the message has been fully delivered.  Any other non-zero  exit  status,  including  abnormal
       termination,  is  interpreted  as the MMDF value RP_MECH (200), which means “use an alternate
       route” (deliver the message to the mail drop).

BUGS
       Only two return codes are meaningful, others should be.

       slocal was originally designed to be backwards-compatible with the maildelivery functionality
       provided by MMDF-II.

nmh-1.8                                      2022-03-13                                  SLOCAL(1mh)