Outlook – e-mails from some people in address book not received and not visible as blocked anywhere

Since I was converted from Hotmail to Outlook I do not receiving  e-mails  any more from one of the people in my address book. The e-mails have left the sender OK, but do not appear in my inbox. They do not seem to appear anywhere, as blocked e-mails etc. I am now concerned how I would know if other people have sent me e-mails which do not seem to appear on any blocked list. Please would someone advise me what to do, and where I can see a list of any e-mails which I have not received.