Written by Cory Wright - corywright gmail.com

You can find the most up to date documentation online at 
http://projects.standblue.net/software/quser/

Tools included with quser.

  * cmaildir
  * validate-sender
  * validate-recipient
  * mybadmailfrom
  * mybadmailto


cmaildir is a short C program for checking Maildir's for 
new mail. If run with no arguments cmaildir checks ~/Maildir/ 
for new mail and also reports messages in the inbox. If 
arguments are passed to cmaildir then it expects them to be 
paths to Maildir style directories, but do not include the 
/cur/ and /new/ portions, the Maildir is the set together. 
I wrote cmaildir because I use Courier-IMAP and it uses 
Maildirs for its folders. I have my list addresses setup to 
go straight into my IMAP folders so with cmaildir I can run 
the following to get a status of all my folders 
(including ~/Maildir/):

  shell$ cmaildir ~/Maildir/.Lists.qmail/ ~/Maildir/.Lists.moto/
  You have 6 new messages, 37 saved

While this may not be that convenient to type at a command 
line, its most useful in a .bash_profile file or as a bash 
alias.


validate-sender is a little C program I wrote because I needed 
to check a sender against a list before allowing it to post to 
an address. I had setup an address for people to add addresses 
to badmailfrom but only wanted certain users to be able to have 
this ability. validate-sender is designed to be called from a 
.qmail file after bouncesaying or condredirect. It takes the 
filename of the list file as an argument. The list file should 
contain a list of addresses or domains, one per line. Domain 
entries can either be in the form @site.dom or site.dom. For 
example:

  |bouncesaying "You are not in my list of allowed senders" validate-sender /etc/badmailadders
  |/usr/local/bin/addtobadmailfrom

Or, with condredirect to alert me when somebody tries to submit:

  |condredirect myemailaddress validate-sender /etc/badmailadders
  |/usr/local/bin/addtobadmailfrom

validate-sender returns 1 if a match is found, and 0 if no match 
is found. 111 is returned if there is an error. I stick validate-sender 
in /var/qmail/bin since the only place it will probably ever be 
used is with qmail. 

Please note that no method is fool proof against forgeries, 
just see what djb has to say. In other words, dont trust your 
system to anything like this, it should only be used for trivial 
checks.


The validate-recipient program is very similar to the validate-sender
program, except it checks against the value of the SMTP envelope recipient 
address. This is mainly for use in .qmail-default files. For example, if 
all of your mail passes through a mail gateway that forwards mail using 
smtproutes then you probably use a .qmail-default file for this. If you 
know in advance the complete list of addresses that should be forwarded 
then you can block anything else from being forwarded.


  |bouncesaying "No mailbox by that name." validate-recipient /path/to/addresses.txt
  |forward "$DEFAULT"@someotherserver.example.com


validate-recipient uses the same exit codes as validate-sender. 

mybadmailfrom is a program that allows individual users to manage 
their own badmailfrom lists. If a user is sick of getting mail from 
a certain address or domain then all they need to do is add it to 
their personal badmailfrom list. Once the list is ready the user can 
add a line to their .qmail file before all the rest:

  |mybadmailfrom ~/Maildir/mybadmailfrom
  ./Maildir/

Although messages from addresses listed in ~/Maildir/mybadmailfrom will
bounce, I should note that this works in a very different way from the 
badmailfrom file that qmail-smtpd uses. Addresses listed in 
/var/qmail/control/badmailfrom are blocked at the SMTP connection. 
Addresses listed in mybadmailfrom must first be accepted into the 
system so that qmail-local can run the .qmail file.


mybadrcptto is useful for blocking certain recipient addresses in a 
.qmail-default file. For example, if you have a qmail gateway that scans 
all mail for spam or viruses and forwards accepted mail onto another server, 
you may want to block certain invalid or expired addresses. The badmailrcpto 
program will allow you to maintain a list of addresses that you dont want to 
pass through:

  |mybadrcptto ~/ex-employees.txt
  |forward "$DEFAULT"@internal.example.com

With this setup any mail sent to an address thats listed in the 
~/ex-employees.txt file will bounce. All other mail will pass through 
and be forwarded to the internal server. There is a patch available for 
qmail that will block certain RCPT TO: addresses at the SMTP conversation. 
The advantage to using mybadrcptto is that 1) you do not need to patch qmail, 
and 2) individual users can implement their own badrcptto lists. The 
disadvantage to using the mybadrcptto program as opposed to the patch is 
that all email must first be accepted into the system, and only then can 
qmail-local run the mybadrcptto program to check the recipient.