Imap client sees folders inside inbox

[#1]

I've just set up a Plusnet mailbox account to be accessed from Mac OSX Microsoft Outlook via IMAP and all of the "system" folders (sent,deleted,drafts,etc) are shown as sub-folders of the INBOX. They don't display this way on PlusNet's webmail (roundcube) and neither do other (non-plusnet) IMAP accounts (e.g. iCloud) when used on the same Outlook client.
Ideally, things like sent, deleted and drafts would exist at the same level as inbox so that the client renders them correctly.
Any ideas why I'm getting this is and can I change it ?
Thanks in advance.

[#2]

That layout is fairly typical of IMAP servers.
With outlook, there is a possibility of changing its behaviour going by this http://www.msoutlook.info/question/619

[#3]

It's the way Thunderbird displays them and so does the old basic webmail (Squirrelmail).

[#4]

Quote from: kmilburn

That layout is fairly typical of IMAP servers. With outlook, there is a possibility of changing its behaviour going by this http://www.msoutlook.info/question/619

I think this looks like the answer but it didn't work when I tried it.
I tried "INBOX" and "Inbox" but neither made any difference. Any ideas?

[#5]

You're seeing this due to the way the namespace is configured for our mail server (Courier). Using Outlook 2007 I was able to flatten the folder hierarchy using 'INBOX' (minus quotes).

. list """*"
* LIST (\HasNoChildren) "." "INBOX.Test"
* LIST (\HasNoChildren) "." "INBOX.Drafts"
* LIST (\HasNoChildren) "." "INBOX.Trash"
* LIST (\HasNoChildren) "." "INBOX.Sent"
* LIST (\HasNoChildren) "." "INBOX.Spam"
* LIST (\Unmarked \HasChildren) "." "INBOX"
. OK LIST completed