I was originally blaming this on our old firewall but getting the same issues even with our shiny new Palo Alto so thinking there's something else at play...

On every other site on t'Internets browsing is fast; Google logins work fine and all seems normal. As soon as you try and login to a Microsoft site e.g. Hotmail, SkyDrive etc it's like wading through treacle. Just get stuck with the loading circle for 30 seconds+

Eventually you get there but everything is still clunky and doesn't feel quite right. Moving between MS services e.g. going from email to SkyDrive takes time with the loading circle again. Are there particular domains \ ports that the authentication system needs to be specifically allowed that it gets narky without being there?

Our part-time students use their own accounts for email for the most part so need to try and speed the login process up as it reflects poorly on the rest of the browsing experience.