Just in case you encounter problems permanently deleting e-mails in Outlook 2007 on an IMAP server, make sure you have the Purge items when switching folders while online option checked (see screenshot below).
What happened was when I tried deleting e-mails, the e-mails would just have a strikethrough line, but would still be present in the inbox; the Purge Deleted Messages button/action (normally under the Edit menu), which should permanently delete the e-mails didn’t do anything.
So keep that in mind. =0)