Tried to sign up for a Hotmail account a few times and seems their signup server/system is down, so I remembered I had an old Yahoo mail address and I reactivated it and added it using the BIS page and still no luck.

In the meantime, O2 told me "Version 4.5 will allow customers to view emails in full HTML format once approved." & "A minority of our customers will have already upgraded to a non O2 approved version of firmware. These customers will not experience difficulties when attempting to receive emails in HTML format, but they will not be able to view this on their Blackberry."