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Showing posts from June, 2011

Eliminating Duplicate Emails during local delivery

Often you will find program like MS outlook, notorious for sending duplicate emails, flooding your inbox. IndiMail allows you to quickly deal with this proprietary nonsense by turning on duplicate eliminator in vdelivermail(8) - the default MDA. To turn on the duplicate eliminator in vdelivermail, you need to set ELIMINATE_DUPS and MAKE_SEEKABLE environment variables.

% su
# echo 1> /service/qmail-send.25/variables/ELIMINATE_DUPS
# echo 1> /service/qmail-send.25/variables/MAKE_SEEKABLE
# svc -d /service/qmail-send.25; svc -u /service/qmail-send.25
# exit

If you do not use vdelivermail and want to use your own delivery agent? Fear not by using ismaildup(1). ismaildup expects the email on standard input and is easily scriptable like the example below in a .qmail file.

   | ismaildup /var/indimail/bin/maildirdeliver /home/manny/Maildir

will deliver mails to /home/manny/Maildir while discarding duplicates.

If you are not happy with the 900 seconds (15 minutes) time interval for checking …

Using procmail with Indimail

IndiMail follows the traditional UNIX philosophy. "Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface" This allows IndiMail to interface with many programs written by others. IndiMail uses a powerful filter mechanism called vfilter(8). You may already be familiar with procmail. procmail is a mail delivery agent (MDA) capable of sorting incoming mail into various directories and filtering out messages. There are three ways in which you can use procmail with IndiMail. 1. inside .qmail Users can use | preline procmail from ~/.qmail. They will need to use a full path for procmail unless procmail is in the system's startup PATH. 2. Edit .qmail-default | preline -f procmail -p -m /var/indimail/etc/procmailrc 3. Have an alias You can use valias(1) to create an alias to call procmail. The following alias calls procmail to deliver the mail using /var/indimail/etc/procmailrc as a pr…

Writing Filters for IndiMail

IndiMail provides multiple methods by which you can intercept an email in transit and modify the email headers or the email body. A filter is a simple program that expects the raw email on standard input and outputs the message text back on standard output. The program /bin/cat can be used as a filter which simply copies the standard input to standard output without modifying anything. Some methods can be used before the mail gets queued and some methods can be used before the execution of local / remote delivery.

It is not necessary for a filter to modify the email. You can have a filter just to extract the headers or body and use that information for some purpose. IndiMail also provides the following programs - 822addr(1), 822headerfilter(1), 822bodyfilter(1), 822field(1), 822fields(1), 822header(1), 822body(1), 822headerok(1), 822received(1), 822date(1), 822fields(1) to help in processing emails.

Let us say that we have written a script /usr/local/bin/myfilter. The myfilter program …

Explanation of email delivery mechanism for local users

Any email that needs to be delivered needs to be put into a queue before it can be taken up for delivery. Email can be submitted to the queue using qmail-queue command or qmail_open() function. The following programs use the qmail_open() API -
condredirect, dot-forward, fastforward, filterto, forward, maildirserial, new-inject, ofmipd, qmail-inject, qmail-local, qmail-qmqpd, qmail-qmtpd, qmail-queue, qmail-send, qreceipt, replier, rrforward, qmail-smtpd.
Of these, qmail-smtpd and qmail-qmtpd accept an email for a domain only if the domain is listed in rcpthosts. Once an email is accepted into the queue, qmail-send(8) decides if the mail is to be delivered locally or to a remote address. If the email address corresponds to a domain listed in locals or virtualdomains control file, steps are taken to have the email delivered locally.
Delivery Mode The delivery mode depends on the argument passed to qmail-daemon during startup. The script /service/qmail-send.25/run passes the content of the f…