In most cases the gift card will arrive just fine in the inbox. However, in some instances Google's Gmail will sort the gift card e-mail differently.

When you log into your Gmail account you are often presented with three tabs in the top of your inbox: 1. Primary, 2. Social and 3. Campaigns. If you don't see the gift card in your inbox then make sure to check all tabs for it.

If you find it, you can move it to your inbox and then you will in the future receive gift cards there as well.