Running Linux, 5th Edition - Matthias Kalle Dalheimer [442]
The final part of the recipe is the text backup, which indicates that the mail will end in the mailbox named backup. If $MAIL/backup is a directory, the mail will be put in a unique named file in that directory (this is known as maildir storage). Alternatively, if $MAIL/backup is a file, the mail will be appended to that file (this is known as mbox storage).
Storing mail from a mailing list in a special mailbox
The next recipe might be what you most often do with Procmail — namely, to save mail from a mailing list into a dedicated mailbox. This is done with a recipe looking like this:
:0:
* Return-Path:.*kde-devel-bounces
kde-devel
Notice that this time we do not use the c flag, because we want mail from this mailing list to stay in the kde-devel mailbox, and not get to our inbox.
The line starting with an asterisk is the condition that must be met for this recipe to be triggered. This line is a regular expression that says that the header of the mail must contain the text Return-Path:, then any text (the regular expression .*), and then the text kde-devel-bounces. We got the idea for this regular expression by looking in an email from the mailing list. The trick is always to find a regular expression that will match any mail from the mailing list, but not match any other mail.
Forward messages as SMS
The following recipe forwards a message with a subject starting with the text SMS to a mobile phone in the form of a text message through an imaginary email-to-SMS gateway.
:0
* < 1000
* Subject: SMS
! 12345678@smsgateway.com
This recipe contains two conditions: the first is that the overall size of the letter be less than 1000 bytes, and the second is that the subject should start with SMS.
The action of this recipe starts with an exclamation mark, which indicates that the message is forwarded to the address following the exclamation mark.
Sending an out-of-office reply
The final example we show is how to send an out-of-office reply. Many systems provide a program named vacation that does this in a fairly robust way, but we provide something more customizable here so you can vary the message in any way your scripting skills allow. The basic recipe looks like this:
:0c
* !^FROM_DAEMON
* !^X-Loop: your@own.mail.address
{
SUBJECT=`formail -zx subject:`
:0
| (formail -r -I"Precedence: junk" \
-A"X-Loop: your@own.mail.address" ; \
echo "I recived the mail with the subject \"$SUBJECT.\""; \
echo "I'm out of the office and will answer it as soon as possible") | $SENDMAIL -t
}
Starting with the conditions again, this recipe sends an out-of-office reply only if (1) the mail is not from a mailer daemon, and (2) the mail does not contain the header line X-Loop:your@own.mail.address (this should, of course, be replaced with your actual email address). The first condition ensures we do not send out-of-office replies to mailing lists, and the second condition ensures we do not end up in a mail loop with someone else's out-of-office filter.
The action to take when these two conditions are met is a block of recipes. Whatever it says in between the braces is interpreted as if it were a normal Procmail script. If execution makes it to the end of the block (i.e., the mail has not yet been delivered), it will continue execution outside the block. This is, however, not the case in our setup.
The first line of the block is an assignment to the variable SUBJECT. The value comes from standard output from the formail command. This is a binary shipped with Procmail; its purpose is to either manipulate the emails or subtract part of them.
The second part of the block is the part that does the core work. It composes an answer and mails it back to the person who originally sent you an email. Let's take it bit by bit.
First we call formail -r to create an auto respond header from the incoming mail. That means that it will throw away headers that you do not want in the reply.