chauncey, as you are YEG based, here is my Canadian perspective.

When I generate referrals I always specify multiple email accounts, across YAHOO, HOTMAIL and GMAIL, so that I'm sure to get the referral email into one of them, and they arrive within 10 minutes (usually, and sometimes even sooner).

For GMAIL, depending on your mail preferences, you may have a "Promotions" tab/filter at the top of the page that you need to click on to see the email. Or, on the left side of my page I see a list of my mail folders and a built-in called "More", which in turn allows me to select "All Mail"...either of these usually (in my case, always) reveal the missing referral email from Amex.