Mick,
The reason is that the website at http://www.softchoice.com/Office365/Guide/Licensing is not configured to ignore parameters it does not understand. When a link is sent in an email, we add parameters to enable identifying who clicked the link and visited the page. It looks like the page at http://www.softchoice.com/Office365/Guide/Licensing cannot handle parameters it doesn't understand instead of ignoring them. For instance, if you just add a random nonsense parameter such as ?x=123 the page does not work either: http://www.softchoice.com/Office365/Guide/Licensing?x=123
This is a website or webpage configuration issue, and looks to be related to the fact that the link is not to an actual page (like default.aspx or licensing.aspx) but to an ASP.NET web application that dynamically renders the page. You can have your web developer research a way to ignore parameters it doesn't recognize or provide a full URL that includes the page address and extension (which still might not ignore parameters it doesn't recognize, depending on the configuration of the website hosting and/or aspx page.)