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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 duplicates, you can change it by setting the DUPLICATE_INTERVAL environment variable. The following will not allow a single duplicate to be entertained within 24 hours

% su
# echo 86400 > /service/qmail-send.25/variables/DUPLICATE_INTERVAL
# svc -d /service/qmail-send.25 ; svc -u /service/qmail-send.25
# exit
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