I've followed this guide to get postfix set up. I've not completed it yet, as from sending test emails, email is no longer being delivered since switching to Maildir from mbox.

I have created a Maildir directory with cur, new and tmp sub directories.

~$ ll
drwxrwxr-x 5 greg greg    4096 2012-07-07 16:40 Maildir/
~$ ll Maildir/
drwxrwxr-x 2 greg greg 4096 2012-07-07 16:40 cur
drwxrwxr-x 2 greg greg 4096 2012-07-07 16:40 new
drwxrwxr-x 2 greg greg 4096 2012-07-07 16:40 tmp

Send a test email.

~$ netcat mail.example.com 25
220 ubuntu ESMTP Postfix (Ubuntu)
ehlo example.com
250-ubuntu
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
mail from: [email protected]
250 2.1.0 Ok
rcpt to: [email protected]
250 2.1.5 Ok
data
354 End data with <CR><LF>.<CR><LF>
Subject: test email

Hi,
Just testing.
.
250 2.0.0 Ok: queued as 56B541EA53
quit
221 2.0.0 Bye

Check the mail queue.

~$ mailq
Mail queue is empty

Check if mail has been delivered.

~$ ls -l Maildir/new
total 0

Some postfix settings:

~$ sudo postconf home_mailbox
home_mailbox = Maildir/
~$ sudo postconf mailbox_command
mailbox_command =

/var/log/mail.log

Jul  7 16:57:33 li305-246 postfix/smtpd[21039]: connect from example.com[178.79.168.xxx]
Jul  7 16:58:14 li305-246 postfix/smtpd[21039]: 56B541EA53: client=example.com[178.79.168.xxx]
Jul  7 16:58:33 li305-246 postfix/cleanup[21042]: 56B541EA53: message-id=<20120707155814.56B541EA53@ubuntu>
Jul  7 16:58:33 li305-246 postfix/qmgr[20882]: 56B541EA53: from=<[email protected]>, size=321, nrcpt=1 (queue active)
Jul  7 16:58:33 li305-246 postfix/smtp[21043]: 56B541EA53: to=<[email protected]>, relay=none, delay=30, delays=30/0.01/0/0, dsn=5.4.6, status=bounced (mail for example.com loops back to myself)
Jul  7 16:58:33 li305-246 postfix/cleanup[21042]: 1F68B1EA55: message-id=<20120707155833.1F68B1EA55@ubuntu>
Jul  7 16:58:33 li305-246 postfix/bounce[21044]: 56B541EA53: sender non-delivery notification: 1F68B1EA55
Jul  7 16:58:33 li305-246 postfix/qmgr[20882]: 1F68B1EA55: from=<>, size=1999, nrcpt=1 (queue active)
Jul  7 16:58:33 li305-246 postfix/qmgr[20882]: 56B541EA53: removed
Jul  7 16:58:33 li305-246 postfix/smtp[21043]: 1F68B1EA55: to=<[email protected]>, relay=none, delay=0, delays=0/0/0/0, dsn=5.4.6, status=bounced (mail for example.com loops back to myself)
Jul  7 16:58:33 li305-246 postfix/qmgr[20882]: 1F68B1EA55: removed
Jul  7 16:58:36 li305-246 postfix/smtpd[21039]: disconnect from domain.me[178.79.168.xxx]
Jul  7 17:10:38 li305-246 postfix/master[20878]: terminating on signal 15
Jul  7 17:10:39 li305-246 postfix/master[21254]: daemon started -- version 2.8.5, configuration /etc/postfix

Any ideas?