Here are some highlights for configuring Postfix to use Courier-Maildrop for local delivery.

This allows some advantages over just having postfix deliver, because you can do server-side filtering of spam and mailing list messages to de-clutter your inbox.

All these notes are based on configuring the setup on Ubuntu 8.10 (Intrepid Ibex) with Debian Lenny’s courier-maildrop

The following are snippets from my configuration files, highlighting the changes that I had to make, from an already existing mail server. If these look unfamiliar, or you need more assistance setting up the basic framework of a Postfix + Courier-IMAP mail server, start here.

So if you have a working mail server: make these changes, sudo /etc/init.d/postfix restart, and then get to work writing your .mailfilters!

Here are the steps that I went through to migrate my Postfix/Courier server from Slicehost to Mosso.

1. Check current DNS MX records for applicable domains. I had mine set to all go through a central A record (my mail server) so it was easy.
2. Set MX records to expire quickly (I think the minimum is 60 minutes). This can take 24 hours to propogate, so do this early, and then you’ll have time to do the rest of the processing.
3. Configure Postfix/Courier/IMAP as desired on new server. There are a lot of howtos on this, and some hints on this site, so I won’t go over how to do this here.
4. Test server to ensure that email can go in and out and that any spam filtering or other processes are operating well.
5. I use MySQL for managing users and forwardings, so I dumped and locked my existing database, and copied that to the new database.
6. Rsync maildirs over from the old server to the new server. This can take a while, depending on server speed and bandwidth.
7. Ensure that Postfix and Courier are up and running on the new server.
8. Change central DNS record to point to new server IP address.
9. Stop Postfix and Courier on old server. This could lead to a couple of bounced emails, but in all likelihood the sending email servers will retry and find their way to the new server.
10. Watch closely.

There should be very little loss of email, connectivity, or data using this path.

If anyone has any better suggestions, let me know.

If you are having issues getting an SSL connection to Courier IMAP. Check your certificate files.

Courier is expecting a PEM file for TLS_CERTFILE with your certificate and private key. Do not use just your certificate.

Also, if you require intermediate certificates to complete the trust chain, you can include them in this file.

MAKE SURE that you have proper permissions on this file to the security of your private key.

If you need postfix to listen on multiple ports (like I do) add lines like the following (replace numbers with whatever ports you desire):

Make sure to open the ports in iptables as well.