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214 Chapter 16. Email

• MAILDIR — Sets the current working directory for Procmail. If set, all other Procmail paths are

relative to this directory.

• ORGMAIL — Speciﬁes the original mailbox, or another place to put the messages if they cannot be

placed in the default or recipe-required location.

By default, a value of /var/spool/mail/$LOGNAME is used.

• SUSPEND — Sets the amount of time, in seconds, that Procmail will pause if a necessary resource,

such as swap space, is not available.

• SWITCHRC — Allows a user to specify an external ﬁle containing additional Procmail recipes,

much like the INCLUDERC option, except that recipe checking is actually stopped on the referring

conﬁguration ﬁle and only the recipes on the SWITCHRC-speciﬁed ﬁle are used.

• VERBOSE — Causes Procmail to log much more information. This option is useful for debugging.

Other important environmental variables are pulled from your shell, such as LOGNAME, which is your

shell.

A comprehensive explanation of all environments variables, as well as their default values, is available

on the procmailrc man page.

16.5.2. Procmail Recipes

New users often ﬁnd the construction of recipes the most difﬁcult part of learning to use Procmail. To

some extent, this is understandable, as recipes do their message matching using regular expressions,

which is a particular format used to specify qualiﬁcations for a matching string. However, regular

expressions are not very difﬁcult to construct and even less difﬁcult to understand when read. Addi-

tionally, the consistency of the way Procmail recipes are written, regardless of regular expressions,

makes it easy to ﬁgure out what is going on.

A thorough explanation of regular expressions is beyond the scope of this chapter. The structure of

Procmail recipes is more important, and useful sample Procmail recipes can be found at various places

on the Internet, including http://www.iki.ﬁ/era/procmail/links.html. The proper use and adaptation of

the regular expressions found in these recipe examples depends upon an understanding of Procmail

recipe structure. Introductory information speciﬁc to basic regular expression rules can be found on

the grep man page.

A Procmail recipe takes the following form:

flags : lockfile-name

* special-condition-character condition-1

* special-condition-character condition-2

* special-condition-character condition-N

special-action-character action-to-perform

Figure 16-9. Structure of a Procmail recipe

The ﬁrst two characters in a Procmail recipe are a colon and a zero. Various ﬂags can optionally

be placed after the zero to control what Procmail does when processing this recipe. A colon after

the flags section speciﬁes that a lockﬁle will be created for this message. If a lockﬁle is to be

created, you specify its name in the

lockfile-name space.

A recipe can contain several conditions to match against the message. If it has no conditions, every

message will match the recipe. Regular expressions are placed in some conditions in order to facilitate

a match with a message. If multiple conditions are used, they must all match in order for an action to

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