The Hotmail hangover continues today with millions of users still having trouble accessing their online email accounts, despite Microsoft claims that the service is now working fine after a three-hour collapse yesterday evening.

The collapse - which also brought down MSN Messenger - affected Microsoft ISP customers and various other Passport services. It was summed up as "log-on and connectivity issues" by Microsoft, but the software giant refused to give any further details, other than it was an internal problem rather than the result of external attack.

Microsoft refuted the suggestion that the problem was the same as one that saw a similar collapse last Friday - that time for eight hours. It refused to give any details about the reasons behind that collapse either, leading some observers to question whether we are getting the whole truth.

The worst-case scenario is that Microsoft's Passport system has a flaw. Passport is crucial to Microsoft's plans since it acts as the cornerstone to its whole Web services push. It stores an array of personal details about a user - including birthday (hence correct horoscopes on visiting MSN.com), credit card details and anything else you choose to share with the company.

The company is heavily pushing it to businesses in order to get a foothold in Internet businesses - for example online auction house eBay is now tied in with it - and is also incorporating it into its software products. Any suggestion that Passport is anything but perfect is immediately met with strong denials by Microsoft, but with regular outages on its flagship Hotmail and the absence of any explanations, speculation will continue to mount.