gurgitate-mail - Online in the Cloud

PROGRAM:

NAME

gurgitate-mail - an easy-to-use mail filter

SYNOPSIS

gurgitate-mail

DESCRIPTION

"gurgitate-mail" is a program which reads your mail and filters it according to the
.gurgitate-rules.rb file in your home directory. The configuration file uses Ruby syntax
and is thus quite flexible.

It's generally invoked either through your .forward file:

"|/path/to/gurgitate-mail"

Or through your .procmailrc file:

:0:
| /path/to/gurgitate-mail

Alternatively, if you're the sysadmin at your site, or your sysadmin is friendly, you can
use gurgitate-mail as a local delivery agent. For postfix, put

mailbox_command=/opt/bin/gurgitate-mail

in /etc/postfix/main.cf. If you use any other MTA, and configure gurgitate-mail as a
local delivery agent, please tell me how! I want to include this in the documentation.

CONFIGURATION FILES

There are three configuration files used by gurgitate-mail: two are system-wide, and the
third, is the user rules file.

The two system-wide configuration files are /etc/gurgitate-rules and
/etc/gurgitate-rules-default. These are processed before and after the user rules,
respectively.

/etc/gurgitate-rules is used to handle system-wide filtering needs: setting the default
mailbox style to Maildir rather than the default MBox, setting the spool directory, things
like that.

The user configuration file is $HOME/.gurgitate-rules (or, alternatively,
$HOME/.gurgitate-rules.rb. Either work). You put your own rules here. If the user
configuration file doesn't encounter a "return" during processing, then the additional
rules contained in /etc/gurgitate-rules-default are run. If that also doesn't return,
then mail messages are saved into the default mail spool location.

If the "-f" option is used on the commandline, then the file specified will be used and
the default rules will not. The "-f" option can be used more than once:

gurgitate-mail -f test-rules -f additional-rules

CONFIGURATION PARAMETERS

There are several parameters that you can set to change the way that gurgitate-mail
behaves. You set a config parameter by saying, for instance:

sendmail "/usr/sbin/sendmail"

which sets the "sendmail" parameter to "/usr/sbin/sendmail".

maildir
The directory you want to put mail folders into. This defaults to $HOME/Mail.

logfile
Where you went gurgitate-mail's log messages to go to. The standard location for
this is $HOME/.gurgitate.log

sendmail
The full path to the sendmail program, used to deliver mail. This can be any program
that takes as its parameters the list of addresses to deliver mail to, and that takes
a mail message on standard input.

homedir
The full path of your home directory. This defaults to whatever your actual home
directory is.

spooldir
The path where the system's mail spools goes to. This defaults to "/var/spool/mail".
On a Maildir system, this should be set to the same as "homedir".

spoolfile
The mail spool file component of the full path of your mail spool. This is generally
your username. Maildir users should set this to "Maildir".

folderstyle
The style of folders you prefer. This can be (at the moment) either MBox or Maildir.

FILTER RULES

The filter rules are a series of Ruby statements, with the following methods and variables
available:

Variables

from This contains the envelope "from" address of the email message. (Note that this
isn't necessarily the same as the contents of the "From:" header)

headers
This is an object containing the headers of the message. There are several methods
that come with this object:

body This contains the body of the email message. As of yet, there's nothing really
interesting which you can do with this, apart from assigning to it; you can rewrite
the body of an email message this way. Dealing with attachments is planned for a
future release of "gurgitate-mail".

maildir
The directory which contains the folders, used by the "save" method when you specify
a folder as "=folder" (like Elm). Defaults to "$HOME/Mail".

homedir
Your home directory. Read-only.

logfile
The location of the "gurgitate-mail" logfile. If set to "nil", then no logging is
done. Defaults to "$HOME/.gurgitate.log".

sendmail
The location of the "sendmail" program. Used by the "forward" method. Defaults to
"/usr/lib/sendmail".

spoolfile
The location of the mail spool. Read-only.

Methods

matches(name(s),regex)
Returns "true" if the header "name" matches the regular expression "regex". If
"name" is an array of header names, then it returns true if at least one of the
headers matches. Useful for testing whether both "To:" and "Cc:" headers match.

from Returns the envelope "from" address of the email message. Note that this is the same
as the bare "from".

to Returns a HeaderBag (a kind of array) with the contents of the "To" and the "Cc"
headers.

to_s As per Ruby convention, returns all the headers as a "String" object.

save(mailbox)
This saves the message to a mailbox. You can specify the mailbox as a word with an =
sign in front of it, in which case it puts it into "maildir". If you don't use the
=name format, then you need to specify an absolute pathname. If it can't write the
message to the file you request it to, it'll attempt to write it to "spoolfile".

forward(address)
This forwards the email message to another email address.

pipe(program)
This pipes the message through "program". "pipe" returns the exit code of the
program that the message was piped through.

filter(program)
This pipes the message through "program" and returns a new Gurgitate object
containing the filtered mail. (This is handy for external filters which modify email
like, for example, SpamAssassin, which adds a spam-score header.)

You can also say

filter(program) do
# code here
end

and it yields the newly-created Gurgitate object to the block.

headers
This returns the headers as an object of their own. This object has its own methods:

headers[*headernames]
This returns a HeaderBag (a subclass of array) containing the headers you asked
for. You can then use the =~ operator on this result to match the RHS regex
with everything in the HeaderBag.

You can change a header's value with "headers[name]=newvalue".

headers.match(name,regex)
Matches the header with the name "name" against the regex. This is the same as
headers[name] =~ /regex/.

headers.matches(names,regex)
Matches the headers with the names "names" against the regex. This is the same
as headers[*names] =~ /regex/.

headers.from
Returns the envelope from. You can change this with "headers.from=newaddress"
too.

return
This tells "gurgitate-mail" to stop processing the email message. If you don't use
"return", then "gurgitate-mail" will continue processing the same mail again with the
next rule. If there isn't a "return" at the end of gurgitate-rules.rb, then
"gurgitate-mail" will save the email message in the normal mail spool.

log(message)
This writes a log message to the log file.

SIMPLE EXAMPLES

Here are some examples of "gurgitate-mail" rules, with explanations:

if from =~ /ebay.com/ then save("=ebay"); return; end

Any email from eBay (automatic end-of-auction notifications, for example, and outbid
notices) gets filed into the "ebay" folder.

if from =~ /root@/ then save("=root"); return; end

Any email from root (at any host) gets filed into a special folder. Useful for sysadmins
monitoring crontab email.

if headers.matches(["To","Cc"],"webmaster@") then
save("=webmaster")
return
end

Any email with a To: or Cc: line of "sysadmin" is saved to a "sysadmin" folder. Useful
for people with multiple role accounts redirected to their address.

if headers["Subject"] =~ /\[SPAM\]/ then
save("=spam")
return
end

This is a different syntax for matching patterns against headers. You can also match
multiple headers in the square brackets.

if headers["Subject","Keywords"] =~ /a bad word/ then
save("=swearing")
return
end

Searches for "a bad word" in the Subject and Keywords headers, and if it's there, saves
the email in the "swearing" folder.

if headers.matches(["To","Cc"],"[email protected]") then
pipe("|rcvstore +mailing-list")
return
end

Any email to a mailing list is piped through "rcvstore" to store it into an MH folder.

That

headers.matches(["To","Cc"],/regex/)

idiom happens often enough that there's a shorthand for it:

if to =~ /[email protected]/ then
pipe("|rcvstore +mailing-list")
return
end

Pipes the mail to the mailing list through "rcvstore".

ADVANCED EXAMPLES

Here are some slightly more clever examples to give you an idea of what you can do with
"gurgitate-mail". Let's suppose you have an email whitelist in a file called
$HOME/.friends, so you can determine whether some email is likely to be spam or not.

Then if someone on your whitelist sends you email, then you automatically save that into
the "inbox" folder:

friends=homedir+"/.friends"
if FileTest.exists?(friends) and FileTest.readable?(friends) then
File.new(friends).each do |friend|
if from =~ friend.chomp then
log "Mail from friend "+friend.chomp
save("=inbox")
return
end
end
end

Okay, if someone sends you email, and it's addressed specifically to you (and gurgitate-
mail hasn't caught it in another form already), then it might or might not be spam: put it
into a "grey" folder:

my_addresses= [ /me@example\.com/i,
/me@example\.org/i,
/me@example\.net/i]; # I have three email addresses
my_addresses.each do |addr|
if headers.matches(["To","Cc"],addr) then
save("=possibly-not-spam")
return
end
end

And after that, if it's not from someone you know, and it's not addressed to your email
address either, then it's probably save to assume that it's spam:

save("=spam")
return

This can be improved by using a Bayesian filter, though; for example, Eric Raymond's
bogofilter program (http://bogofilter.sourceforge.net) can be automatically trained and
used with the help of the white/grey/black distinctions. Taking the example above, I'll
adjust it by adding in calls to bogofilter:

friends=homedir+"/.friends"
if FileTest.exists?(friends) and FileTest.readable?(friends) then
File.new(friends).each do |friend|
if from =~ friend.chomp then
log "Mail from friend "+friend.chomp
pipe("bogofilter -h") # <-- LINE ADDED HERE
save("=inbox")
return
end
end
end

"bogofilter -h" trains bogofilter that mail from whitelisted-people is not to be
considered spam. Okay, at the end of the .gurgitate-rules, change

save("=spam")
return

to

save("=spam")
pipe("bogofilter -s")
return

This trains "bogofilter" that anything which doesn't pass the rest of the filter should be
considered spam. Now for the interesting bit: Change the bit between these to use
"bogofilter" to decide whether email is to be considered spam or not:

my_addresses= [ /me@example\.com/i,
/me@example\.org/i,
/me@example\.net/i]; # I have three email addresses
my_addresses.each do |addr|
if headers.matches(["To","Cc"],addr) then
if pipe("bogofilter")==1
then
log("bogofilter suspects it might not be spam")
save("=possibly-not-spam")
else
log("bogofilter thinks it's probably spam")
save("=spam")
end
return
end
end

"bogofilter" has an exit code of "1" if it thinks the message is not spam, and "0" if it
thinks the message is spam.

Hopefully this should give you an idea of the kinds of things that you can use
"bogofilter" for.

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