Have you tried logging in from the web interface to see if the emails are arriving? I am assuming you have emails from Hotmail, live mail or outlook.com and so going to the web interface should be your first port of call to check if the emails are in "Junk Email" folder.
If your email is with somebody else like yahoo or gmail or aol then try their web-based interface as well.
If you still can't see the email then try checking whether you have blocked ASDA in your filters list. You can check this by going to the web interface again.