FF does make a really pertinent point here.

Most email service providers (Microsoft, Google, Yahoo etc.) don’t have to read every email that is written, although in theory, they could if they really wanted to and had the time.  The have generated a way so that they can electronically sort out emails and filter certain types into the junk mail box.  The first thing they look for are trigger words, and phrases.  So if the email includes words such as ‘free offer’ or ‘special discount’ they are likely to be sent to your Junk mail box rather than your inbox.  They also filter out emails which have come from an address that is not in your email address book, or that you have never received an email from before.  There are lots more filters that are used but this is the simple explanation.  

So we suggest that if you are expecting an email that has not arrived – check your spam or junk mail.