I'm not sure how this differs...

...from the service offered now by simplymailsolutions.com, who provide both hosted Zimbra and Exchange services to individuals and small businesses, right up to dedicated Exchange servers for enterprises.

After a long time flitting between various free email providers, I now use their Zimbra solution (which sounds pretty much identical to the 01.com offering John Latham mentions, right down to the price) and I can't see myself moving away. Everything's synced everywhere from Evolution to my mobile phone to the web, calendar, contacts, tasks... it's bliss!