Helpdesk software with MS CRM 4.0

My company is looking at upgrading from MS CRM 3 to CRM 4. We also require a Helpdesk software package, with normal helpdesk functions in addition to four key features.
1. Integrates with CRM 4 for customer base and record storage.
2. Web based, low bandwdith UI (staff are distributed around the global)
3. Automatic processing of Help email into queue
4. Customer web interface.

Any recommendations?