Not all Hotmail accounts can be Popped (retrieved in an email client), these are very old hotmail account that can be, the newer hotmail accounts, you have to pay for this service.

 

Have you ever popped these hotmail accounts in the past???

I have been able to retrieve my MSN messages into Outlook and Outlook Express in the past.  I can still get them in Outlook, but not OE.  Neither one synchronizes with Plaxo online.