autorespond
Copyright 1998 Eric Huss

2/13/98 - First release.
2/14/98 - Fixed file descriptor bug (wouldn't work on BSD/Linux)

Simple autoresponder for qmail.

==============================================

Here is an autoresponder I wrote for qmail.  The motivation to write this
autoresponder is that it is very difficult to catch loops with an
autoresponder if you set the address of the auto-response the same as the
address of the autoresponder.  Example: 

Mail is sent to help@my-company.com. An automatically generated response
is sent back to the user with an address of "help@my-company.com".  You
can set the envelope sender to an empty string.  However, some programs
will parse the message for the "From:"  field and send an autoresponse
back to it.  It is received at your autoresponder, and you now have a mail
loop. 

This autoresponder also catches some other simple situations such as mail
from a mailer-daemon, empty envelope sender, bulk precedence headers, etc. 

Setting up the Autoresponder
============================

There are two different autoresponders included in this package.
The first one is autorespond.c.  This version uses a simple directory
storage technique to log incoming mail.

The second one is autorespond_mysql.c.  This version uses the popular
MySQL database to log incoming mail.  May be a bit of overkill, but nice
if you don't want to mess with files on busy sites. 

autorespond.c
=============

First thing, if your qmail distribution is not in /var/qmail, then go edit
line 39 to point to the correct directory.  There shouldn't be anything
else to configure.  Compile: 

gcc -Wall -o autorespond autorespond.c

Or whatever you wish (cc, optimizations, etc.)  Should for the most part
compile without warnings. 

Usage is as follows:

autorespond time num message dir

     time - amount of time to consider a message (in seconds)
     num - maximum number of messages to allow within time seconds
     message - the filename of the message to send
     dir - the directory to hold the log of messages

So for example, in your ~alias directory, create a .qmail-help file with
the following:

|autorespond 10000 5 help_message help_autorespond
&your-email-address@company.com

This will allow up to five messages within about 3 hours.

Create a file in your ~alias directory called help_message.  It should say
something like this: 

From: Support <help@company.com>
Subject: Help Response

This is a response to your help request.


Below is a copy of the message we received.

--------

Make sure that "From:" is the first line of the file.  You should probably
include the dashes to separate your help message from the user's message. 
An example is included with this package. 

Create a directory called help_autorespond in your ~alias directory.  This
is where the log of messages goes. 

That should be it.

autorespond_mysql.c
===================

First thing, if your qmail distribution is not in /var/qmail, then
go edit line 39 to point to the correct directory.  You can also change
the database name, user, and password at the top of the file.
Compile:

gcc -Wall -L/var/mysql/lib/mysql -I/var/mysql/include/mysql \
	-o autorespond autorespond_mysql.c -lmysqlclient -lnsl -lsocket -lm

Or whatever you wish (cc, optimizations, etc.)  Should for the most part
compile without warnings.  The -lnsl -lsocket is a Solaris thing.  Don't
use it if you don't need it.  Change the directories to point to your
installation of MySQL.  You'll probably also want to do: 

strip autorespond

This will get the file size down a little with the MySQL libraries.

Usage is as follows:

autorespond time num message

Same as above, but without the directory parameter.

The following is assuming you used the default database names.

Create the MySQL database:

mysqladmin create autoresponder

Create a user called "autoresponder".  By default this should have a blank
password, though you probably should change that. 

Create the table:

mysql autoresponder

CREATE TABLE autoresponder (
  e_mail CHAR(127) NOT NULL,
  time_sent INT UNSIGNED NOT NULL
)


That should be it.

Notes
=====
- If the maximum count has been reached, then the message is not
forwarded on to you.  If you wish to change this behavior, change
_exit(99);   on line 455 for mysql, 440 for the normal one
to:
_exit(0);


- The message sent out has a blank envelope sender.  Some mail systems
reject mail with a blank sender.  If you find this a problem, edit the
line that calls send_message() at the bottom of the program to contain an
envelope address of your choice. 

My apologies from the messy documentation and code.  I normally use
company libraries to write most things, so this was rather clumsily
written with standard c libraries.  If you find a problem or have a
suggestion, please e-mail me at:  e-huss@netmeridian.com

If you wish to clean up the code to compile better on different platforms,
please send me the changes.