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The almost forgotten art of procmail with fetchmail

A friend has set up a POP3 server for one of my domains. So this was a nice trigger to start remembering how I used to use POP for email.

On my diskless OpenBSD 5.7 machine I installed fetchmail, procmail and mutt and started playing with it.

I simply installed fetchmail, procmail and mutt with the pkg_add command.

Fetching and processing mail just like in the old days

Procmail is a very powerful tool that kind do all kind of email magic. We will only touch the surface here.

Using fetchmail to retrieve email

The first thing I do is fetch my email, deleting it on the POP3 server.

The most simple way to use fetchmail is to setup a .fetchmailrc file in your $HOME directory and run fetchmail.

The .fetchmailrc contains something like this:

set postmaster "matto"
set logfile /home/matto/.fetchmail.log

poll pop3.example.com protocol pop3:
    username "<user>" password "<password>";

mda "/usr/local/bin/procmail -d %T"

The first line is to make sure all mail comes to my user, which is "matto". The second line is to keep a log.

The third line contains the name of the POP3 server. The fourth line contains the username ans password for the POP3 server.

The last line tells fetchmail to forward all incoming mail to procmail. The path depends on the system you have, on OpenBSD is it /usr/local/bin/.

Using procmail to filter your email

Next, setup a .forward file in your $HOME directory:

|/usr/local/bin/procmail

All this .forward file does is telling that mail should be processed by procmail. Again, check the path.

Now the magic begins.

Create a .procmailrc file in your $HOME directory:

SHELL=/bin/sh
PATH=/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin
MAILDIR=$HOME/Mail
DEFAULT=$MAILDIR/junk
LOGFILE=$HOME/.procmail.log
LOG=""
VERBOSE=yes

:0:
* ^Subject.*SPAM
$MAILDIR/spam

:0:
* ^(To|Cc).*user@example.com
$MAILDIR/inbox

This .procmailrc file contains a block with some settings followed by two procmail recipes.

This .procmailrc file does several things.

  • It tells procmail which shell and which path-settings to use
  • It tells procmail that my mailboxes line in the $HOME/Mail directory
  • It tell procmail to use the default mailbox "junk" to deliver the mail in
  • It tells procmail to use the mailbox "spam" to deliver all mail in with in the subjectline the word "SPAM"
  • It tells procmail to use the mailbox "inbox" to deliver all mail that is sent to user@example.com

Spammers use all kind of usernames before the @example.com, this way they all end up in the "junk" mailbox, except the ones addressed directly to me (here: user@example.com).

After running this for a few days, you add a spam recipe with something like this:

:0:
* ^X-Spam-Status: Yes
/dev/null

This will send all email that has a line which starts with "X-Spam-Status: Yes" to /dev/null, which is a geeky way of telling to destroy it.

If you are following mailing-lists, it might be a good idea to add a filter for those lists. Example:

:0:
* ^To.*linux@lists.nllgg.nl
$MAILDIR/linux

All mail sent to this list will be collected in the mailbox "linux". Now you can tell Mutt to use its powerful mailinglist-features on this mailbox.

You can add as many as procmail-recipes as you want. They can be very powerful.

Use Mutt to read and write email

Mutt is the most powerful email client

Add some lines to your .muttrc to let Mutt knows where your mailboxes are:

set spoolfile = "$HOME/Mail/inbox"
set folder="$HOME/Mail"      # Local mailboxes stored here
set mbox_type=mbox           # Mailbox type
mailboxes \
~/Mail/=inbox \
~/Mail/=junk \
~/Mail/=spam

The default keybinding to change to a different mailbox in Mutt is 'c', so this is how you can go from the inbox to the other mailboxes.

Resources

Here are some nice reads that helped me setup my procmail/fetchmail system.

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