Outlook can't receive unless I delete emails?

[SK5AG]

Dear all,

when I hit Send/Receive button, I get the 'Send/Receive progress'
notification at the bottom of the outlook window. after completion nothing
shows up in any of my Outlook Personal Folders.
i.e: my webmail inbox shows thet I have 4 unread emails. When I click the
Send/Receive button, the notification at the bottom of the page outlook
window shows that 4 message downloaded sucessfully. however, when i check
the inbox, junk, etc, I can not find the received mail.

if at this point I go ahead and delete one of the emails, I can start
receiving the new once.

please help.