I've setup the form to act as a reservation form for a restaurant. They've updated the form to use their own domain hosted by Hotmail but aren't receiving any emails. I changed the form to send to my own Gmail address and the emails came through immediately.
I wonder if I need to add an SPF record to their domain? I'm not sure what the IP would be though? Any advice would be great!
PS: I have check and the emails are not in their spam folder.