qmail and vpopmail problem

Hi Everybody,
I'm in a problem regarding QMail and VPOPMail.
I've configured my Mail Server with QMail. The POP3 and SMTP both Server address is -
( mail.abc.com ).
And it is working perfectly.No problem at all.

Now I've to host a Virtual Server which is
( www.xyz.org ). I've made it also and I can browse the Web address using http://www.xyz.org. And the MX record also working perfectly.

Now I want to access mails of www.xyz.org which is virtual. I ve used VPOPMail and have added the virtual host xyz.org in /home/vpopmail/domains/ using the command
( ./vadddomain xyz.org ) and added user sandy through the command ( ./vadduser sandy ).

Now from Outlook Express when I'm trying to receive mails for ( sandy@xyz.org ) , I'm getting an error msg. that " Authorization failed " for sandy@xyz.org but I can send mails from
( sandy@xyz.org ). and when I'm checking the new folder inside the Maildir of sandy (sandy@xyz.org) in vpopmail I can see the message which is sent from other mail address say ( sandy@abc.com ).

Please help me out of this situation. please let me know where I did mistake or which thing I've slipped out.