This is a very simple script that sends you an e-mail if you don't get an answer to an e-mail within a deadline.

It is designed to integrate with the exim MTA.

It can be seen as a self-hosted version of followupthen.com.

1. Configure remindmail
2. When you want to be reminded about an unanswered e-mail, add in Bcc rm.*@mydomain.com, where * is a time span from now. The time span can be 2s for "two seconds" or 3d for "three days" (see pytimeparse). If you don't get an answer by then, you will receive an answer to that e-mail to remind you that you need an answer.

The key idea is to have your MTA to feed to the script all the incoming and outgoing e-mail. If an e-mail is addressed to [email protected], the Message-ID of the e-mail is recorded in a database along with a deadline (in this case, two days from now).

If an e-mail has a In-Reply-To header which matches one of the Message-IDs recorded in the databases, the corresponding entry is removed.

If after the chosen deadline, no answer has been received, a notification e-mail is sent to the sender.

In order to use remindmail you need to 1) configure exim so that feeds all the e-mails to the script and 2) set up a cron job to send out notifications.

git clone https://github.com/aleclearmind/remindmail.git /etc/exim4/remindmail/

This script is designed to be run as an "antivirus" from exim. Uncomment the av_scanner directive in your exim.conf file as follows:

av_scanner = cmdline:/etc/exim4/remindmail/remindmail.py \
                         --db /var/mail/remindmail.db \
                         --domain mydomain.com \
                         %s \
                    :nopenope:nopenope

Make sure /var/mail/remindmail.db can be read and written by the exim's daemon user. Note that also the containing directory needs to be writeable, since the sqlite creates lock files.

You should also what follows:

acl_smtp_data = acl_check_data

acl_check_data:
  deny    malware    = *
          message    = This message contains a virus ($malware_name).
  accept

This enables the av_scanner, which is otherwise ineffective. Note however that this script will always return true. Therefore, it will never block any e-mail.

Simply add a cron job:

cat > /etc/cron.hourly/remindmail <<eof
#!/bin/bash
/etc/exim4/remindmail/remindmail.py \
    --domain mydomain.com \
    --db /var/mail/remindmail.db \
    --check
eof
chmod +x /etc/cron.hourly/remindmail

• The recipient of the e-mail won't know anything about remindmail, as long as you employ the Bcc header.
• The chosen SMTP server for sending e-mail is supposed to authorize any e-mail. This makes sense if you have a rule to accept any e-mail from 127.0.0.1 and the script is running on the same machine as the SMTP server.
• The database only records three things: the sender who wants to be notified, the Message-ID and the deadline. Nothing else is recorded.

You can print the database contents as follows:

/etc/exim4/remindmail/remindmail.py \
    --domain mydomain.com \
    --db /var/mail/remindmail.db \
    --print-db