I received one of these last month and just ignored it, assuming it was a scam of some sort.
But today I just received another one. However this one included TWO gift card numbers, one with my first name associated with is, and one with my husband's.
The chances of an automatic spammer having both of our names is pretty unlikely.
The only thing I can think of is that I purchased tickets a few months ago for YYZ-YVR and YVR-YYZ in premium economy for next week. For the first leg the PNR was only for me, but for the second leg the PNR was for the two of us. Perhaps they are giving out gift cards for the "inconvenience" of changing the Premium Economy booking to a Latitude fare? (although in the end that worked out better for us, but that's a different story).
I tried checking on-line for the gift card balance, but I get the error: "Card balance unavailable. The card number you entered may be incorrect, has no available history, or is a promotional card for which balance information is not available or has expired."