Inbox folder is not synchronized via IMAP in Outlook 2003 but all other folders work

Inbox folder is not synchronized via IMAP in Outlook 2003 but all other folders work

I installed my Zoho account in Outlook 2003 (Windows 7 - 64bit)
there are no failure/error messages while synchronization and also all folders are getting synchronized except the inbox!

What can I do to solve the problem?

To explain you the problem better I made some screen shots - see attached!

thank you so much in advance for help!

kind regards
Stephan