Chapter 15. Email

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:0:

* ^(From|CC|To).*tux lug

tuxlug

Any messages sent from the

tux lug@domain.com

mailing list will be placed in the

tuxlug

mail 

box automatically for your MUA. Note that the condition in this example will match the message if it

has the mailing list's email address on the

From

,

CC

, or

To

lines.

Procmail can also be used to block spam, although this is not a good long term solution for junk mail.

The following example illustrates a temporary spam filtering solution, where multiple recipes are set

to use a common mailbox to store the junk.

SPAM=junk

:0:

* To??^$

$SPAM

:0:

* ^(To|CC):.*,.*,.*,.*,.*,.*,.*,.*,.*,.*,.*,

$SPAM

:0:

* ^Message Id:.* [^@]*

$SPAM

In this example, the

junk

mailbox is associated with the

SPAM

variable, so that you can change the

mailbox that holds your spam in one place. Then, three recipes look for messages to send to the

junk

mailbox.

The first recipe looks for messages that have no recipient in the

To

line. The second recipe matches

any messages with 12 or more recipients. The third recipe looks for messages with a bad message ID.

These simple examples are provided to help get you started creating recipes. Consult the many Proc 

mail online resources available from Section 15.7 to see more detailed and powerful recipes.

15.6. Security

Like any other service that flows over a network unencrypted, important email information, such as

usernames, passwords, and entire messages, may be intercepted and viewed, all without the knowl 

edge of the email server or client. When using standard POP and IMAP protocols, all authentication

information is sent "in the clear," meaning that someone on a network between the client and the

remote server can easily view it.

15.6.1. Secure Email Clients

Thankfully, most Linux MUAs designed to check email on remote servers support SSL to encrypt

messages as they are sent back and forth over the network. In order to use SSL when retrieving email,

it must be enabled on the email client and server.

SSL is easy to enable on the client side, often done with the click of a button in the MUA's configura 

tion area. Secure IMAP and POP have known port numbers (993 and 995, respectively) that the MUA

will use to authenticate and download messages.

Popular MUAs included with Red Hat Linux, such as Mozilla Mail,

mutt

, and

pine

, offer SSL 

encrypted email sessions.