Configuring Exim4 to work with Courier as a IMAP server.
This howto was completed on a Debian Linux box, success on other linux flavors may vary.

First install courier-imap and courier-imap-ssl on your mail server.

# apt-get install courier-imap 

# apt-get install courier-imap-ssl 

Next create the Maildir in /etc/skel/ so future users added to the server will have the correct mail settings.

# maildirmake /etc/skel/Maildir 

Edit the file /etc/exim4/update_exim4.conf.conf and add:

dc_localdelivery=maildir_home 

Create the file: /etc/exim4/conf.d/transport/55_courier_transport and add the following to the file:

local_delivery:

driver = appendfile

group = mail

mode = 0660

mode_fail_narrower = false

envelope_to_add = true

return_path_add = true



directory=${home}/Maildir

maildir_format = true

Restart exim4.

# /etc/init.d/exim4 restart 

Restart Courier-IMAP.

# /etc/init.d/courier-imap restart