cannot purge emails in Outlook 2000

[bck]

Using Outlook 2000 on Windows XP, I am experiencing a problem with
emails. There is an IMAP account and up until now the usual method of
deleting emails has worked i.e. 'delete' puts a line through the email
and 'purge' gets rid of it.

However, now 'purge' does nothing and the emails remain (with a line
through). Any ideas about why this is happening? As far as I know
there have been no changes made to the setup.

Thanks in advance

BCK