I came across this issue today as well. There doesn't seem to be any consistency because out of half a dozen attempts to upload users, one worked and 5 didn't. Here's the bounce email where the server tries to append the domain to the address. What's interesting is that the username is shows the email address with some random number after it instead of the username.
The original message was received at Mon, 13 Sep 2010 18:00:04 +1000
----- The following addresses had permanent fatal errors -----
(reason: 550 5.1.1 <email@example.com>... User unknown)
(expanded from: d0e96b79469d6e6478bddab875a8b31b)
----- Transcript of session follows -----
... while talking to [127.0.0.1]:
<<< 550 5.1.1 <firstname.lastname@example.org>... User unknown
550 5.1.1 d0e96b79469d6e6478bddab875a8b31b... User unknown
<<< 503 5.0.0 Need RCPT (recipient)
Reporting-MTA: dns; mail.traininggroup.com.au
Arrival-Date: Mon, 13 Sep 2010 18:00:04 +1000
Final-Recipient: RFC822; email@example.com
Remote-MTA: DNS; [127.0.0.1]
Diagnostic-Code: SMTP; 550 5.1.1 <firstname.lastname@example.org>... User unknown
Last-Attempt-Date: Mon, 13 Sep 2010 18:00:05 +1000
From: "Administrator " <email@example.com>
Date: 13 September 2010 6:00:04 PM AEST
Subject: Site: New User Account
Hi Anthony James,
An online training account has been created at 'World Vision Australia' using
your email address and you now have access to log in and commence training. The
username you have been allocated will remain yours for the duration of your
access to the site and you have been issued a temporary password. When you
first log in to the online site you will be prompted to change your password.
Your current login information is:
To start using 'Site', login at
In most mail programs, this should appear as a blue link which you can just
click on. If that doesn't work, cut and paste the address into the address line
at the top of your web browser window. You DO NOT need to type in www at the
start of the site address.
If you need help, please contact the site administrator.