I have multiple e-mail addresses. Especially with my mail.com e-mail address, sometimes I just never receive e-mails from Hilton or Marriott - even in my spam folder. I don't know why. So I put a different e-mail on the account, and I don't have any problems.
There are people with more computer experience than I have on this board. But from what I understand, most e-mail servers filter out a lot of spam that doesn't even make it to our spam folders. My company has a white list for our server so that this first wave of spam control doesn't filter out an e-mail domain that we want to hear from. I don't have access to that white list, but I have to tell corporate IT to add a domain to it when I don't get e-mails at all - even to the spam folder.
So all of this is just to recommend using a different e-mail address. Marriott could be sending it. But there are different ways it can get held up between Marriott and your e-mail account. It might not be Marriott's fault.