Thanks for a great guide. I'm almost there and I think I have a reasonable understanding of how everything hangs together thank to this.

However, courier-imap doesn't seem to be able to create the mail directories by itself. Am I wrong in thinking that it should? If I'm not, any ideas as to why it is failing?

When I try to get email from the imap account samwise@hydrus.xx.xx, I see the following. Database back end is retrieving all the right values and authentication succeeds.

Jan 22 22:01:17 hydrus imapd-ssl: Connection, ip=[::ffff:xx.156.116.xx]
Jan 22 22:01:18 hydrus imapd-ssl: samwise@hydrus.xx.xx: chdir(/var/mail/vmail) failed!!
Jan 22 22:01:18 hydrus imapd-ssl: error: No such file or directory
Jan 22 22:01:18 hydrus imapd-ssl: LOGIN FAILED, method=PLAIN, ip=[::ffff:xx.156.116.xx]
Jan 22 22:01:18 hydrus imapd-ssl: authentication error: No such file or directory

hydrus ~# ls -la /var/mail/
total 8
drwxrwxr-x 2 root mail 4096 Jan 13 16:16 .
drwxr-xr-x 5 root root 4096 Jan 15 19:51 ..

However, when I create the directories manually (all gid mail and group writable), it goes beyond that, but mail client says "unable to open this mailbox"

Any hints are greatly appreciated