path: root/maildrop/maildropex.sgml

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<refentry id="maildropex">
  <info><author><firstname>Sam</firstname><surname>Varshavchik</surname><contrib>Author</contrib></author><productname>Courier Mail Server</productname></info>

  <refmeta>
    <refentrytitle>maildropex</refentrytitle>
    <manvolnum>7</manvolnum>
    <refmiscinfo class='manual'>Double Precision, Inc.</refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>maildropex</refname>
    <refpurpose>maildrop filtering language examples</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <informalexample>
      <simpara>
<filename>$HOME/.mailfilter</filename>,
<filename>$HOME/.mailfilters/*</filename>
</simpara>
    </informalexample>
  </refsynopsisdiv>

  <refsect1 id="maildropex_description">
    <title>DESCRIPTION</title>

    <para>
If <filename>$HOME/.mailfilter</filename> exists, filtering instructions in
this file will be carried out prior to delivering the message. The filtering
instructions may
instruct <command>maildrop</command> to discard the message, save the
message in a
different mailbox, or forward the message to another address. If
<filename>$HOME/.mailfilter</filename> does not exist,
or does not provide explicit delivery
instructions, <command>maildrop</command> delivers the message to the
user's system mailbox.</para>

    <para>
The files in <filename>$HOME/.mailfilters</filename>
are used when <command>maildrop</command> is
invoked in embedded mode.</para>
  </refsect1>

  <refsect1 id="maildropex_examples">
    <title>EXAMPLES</title>

    <para>
Take all mail that's sent to the 'auto' mailing list, and save it in
<filename>Mail/auto</filename>. The 'auto' mailing list software adds a
"<literal>Delivered-To: auto@domain.com</literal>" header to all messages:
    </para>
    <blockquote>
      <informalexample>
	<programlisting format="linespecific">
if (/^Delivered-To: *auto@domain\.com$/)
    to Mail/auto
</programlisting>
      </informalexample>
    </blockquote>
    <para>
After the <command>to</command> command delivers the message,
<command>maildrop</command> automatically
stops filtering and terminates without executing the subsequent instructions
in the
<systemitem class="resource">filter file</systemitem>.</para>

    <para>
Take all mail from <email>boss@domain.com</email> about the current project
status, save it in <filename>Mail/project</filename>, then forward a copy to
John:</para>

    <blockquote>
	<informalexample>
	  <programlisting format="linespecific">
if (/^From: *boss@domain\.com/ \ 
    &amp;&amp; /^Subject:.*[:wbreak:]project status[:wbreak:]/)
{
    cc "!john"
    to Mail/project
}
</programlisting>
	</informalexample>
      </blockquote>
    <para>
Note that it is necessary to use a backslash in order to continue the
<command>if</command> statement on the next line.</para>

    <para>
Keep copies of the last 50 messages that you received in the
<filename>maildir</filename>
directory 'backup'. NOTE: 'backup' must be a <filename>maildir</filename>
directory, not a
mailbox. You can create a <filename>maildir</filename> using the
<command>maildirmake</command>
command.</para>

<blockquote>
	<informalexample>
	  <programlisting format="linespecific">
cc backup
`cd backup/new &amp;&amp; rm -f dummy \`ls -t | sed -e 1,50d\``
</programlisting>
	</informalexample>
      </blockquote>
<para>
Put this at the beginning of your filter file, before any other filtering
instructions. This is a good idea to have when you are learning
<command>maildrop</command>. If you make a mistake and accidentally delete a
message, you
can recover it from the backup/new subdirectory.</para>

    <para>
Save messages that are at least 100 lines long (approximately) into
<filename>Mail/IN.Large:</filename>:</para>

<blockquote>
	<informalexample>
	  <programlisting format="linespecific">
     if ( $LINES &gt; 100 )
        to Mail/IN.Large
</programlisting>
	</informalexample>
      </blockquote>

    <para>
Send messages from the auto mailing list to the program 'archive', using a
lock file to make sure that only one instance of the archive program will be
running at the same time:</para>

<blockquote>
	<informalexample>
	  <programlisting format="linespecific">
     if (/^Delivered-To: *auto@domain\.com$/)
        dotlock "auto.lock" {

               to "|archive"
        }
</programlisting>
	</informalexample>
      </blockquote>

    <para>
Check if the <literal>Message-ID:</literal> header in the message is identical
to the same header
that was recently seen. Discard the message if it is, otherwise continue to
filter the message:</para>

    <blockquote>
	<informalexample>
	  <programlisting format="linespecific">
`reformail -D 8000 duplicate.cache`
if ( $RETURNCODE == 0 )
    exit
</programlisting>
	</informalexample>
      </blockquote>
    <para>
      The <ulink url="reformail.html">reformail</ulink> command maintains a
      list of
      recently seen Message-IDs in the file
      <filename>duplicate.cache</filename>.
    </para>

    <note>
      <para>
	Unlike a similar feature in the <command>formail</command> command,
	<ulink url="reformail.html">reformail</ulink> takes care of locking
	the file, so it's not necessary to implement your own locking
	mechanism for this option.
      </para>
    </note>

    <para>
Here's a more complicated example. This fragment is intended to go right
after the message has been filtered according to your regular rules, and just
before the message should be saved in your mailbox:</para>

    <blockquote>
	<informalexample>
	  <programlisting format="linespecific">
cc $DEFAULT
xfilter "reformail -r -t"
/^To:.*/
getaddr($MATCH) =~ /^.*/;

MATCH=tolower($MATCH)
flock "vacation.lock" {
        `fgrep -iqx "$MATCH" vacation.lst 2&gt;/dev/null || { \
                  echo "$MATCH" &gt;&gt;vacation.lst ; \
                  exit 1 ; \
              } `
}
if ( $RETURNCODE == 0 )
   exit
to "| ( cat - ; echo ''; cat vacation.msg) | $SENDMAIL"
</programlisting>
	</informalexample>
      </blockquote>

    <para>
This code maintains a list of everyone who sent you mail in the file called
<filename>vacation.lst</filename>.
When a message is received from anyone that is not already on
the list, the address is added to the list, and the contents of the file
<filename>vacation.msg</filename> are mailed back to the sender.
This is intended to reply notify
people that you will not be answering mail for a short period of time.</para>

    <para>
The first statement saves the original message in your regular mailbox.
Then,
<ulink url="maildropfilter.html#xfilter"><command>xfilter</command></ulink>
is used to generate an
autoreply header to the sender. The <literal>To:</literal> header in the
autoreply - which was
the sender of the original message - is extracted, and the <ulink url="maildropfilter.html#getaddr"><command>getaddr</command></ulink>
function is used to strip the
person's name, leaving the address only. The file 
<filename>vacation.lst</filename> is checked,
using a lock file to guarantee atomic access and update (overkill, probably).
Note that the backslashes are required.</para>

    <para>
If the address is already in the file, <command>maildrop</command> exits,
otherwise the
contents of <filename>vacation.msg</filename> are appended to the autoreply
header, and mailed out.</para>

    <note>
      <para>
An easier to make a vacation script is with
<ulink url="mailbot.html"><citerefentry><refentrytitle>mailbot</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>.</para>
    </note>

    <para>
Here's a version of the vacation script that uses a GDBM database file
instead. The difference between this script and the previous script is that
the previous script will send a vacation message to a given E-mail address
only once. The following script will store the time that the vacation message
was sent in the GDBM file. If it's been at least a week since the vacation
message has been sent to the given address, another vacation message will be
sent.</para>

    <para>
Even though a GDBM database file is used, locking is still necessary
because the GDBM library does not allow more than one process to open the same
database file for writing:</para>

<blockquote>
	<informalexample>
	  <programlisting format="linespecific">
cc $DEFAULT
xfilter "reformail -r -t"
/^To:.*/
getaddr($MATCH) =~ /^.*/;
MATCH=tolower($MATCH)
flock "vacation.lock" {
    current_time=time;
    if (gdbmopen("vacation.dat", "C") == 0)
    {
       if ( (prev_time=gdbmfetch($MATCH)) ne "" &amp;&amp; \
             $prev_time &gt;= $current_time - 60 * 60 * 24 * 7)
       {
           exit
       }
       gdbmstore($MATCH, $current_time)
       gdbmclose
    }
}
to "| ( cat - ; echo ''; cat vacation.msg) | $SENDMAIL"
</programlisting>
	</informalexample>
      </blockquote>

    <para>
This script requires that <command>maildrop</command> must be compiled with
GDBM
support enabled, which is done by default if GDBM libraries are present.</para>

    <para>
After you return from vacation, you can use a simple Perl script to obtain
a list of everyone who sent you mail (of course, that can also be determined
by examining your mailbox).</para>

  </refsect1>
  <refsect1 id="maildropex_see_also">
    <title>SEE ALSO</title>

    <para>
<ulink url="maildrop.html"><citerefentry><refentrytitle>maildrop</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>,
<ulink url="maildropfilter.html"><citerefentry><refentrytitle>maildropfilter</refentrytitle><manvolnum>7</manvolnum></citerefentry></ulink>,
<ulink url="reformail.html"><citerefentry><refentrytitle>reformail</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>,
<ulink url="mailbot.html"><citerefentry><refentrytitle>mailbot</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>,
<citerefentry><refentrytitle>egrep</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>grep</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sendmail</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
</para>
  </refsect1>
</refentry>