Hi there @NM12345!
Don here from Shopify. :)
If you find that a given email provider is not permitting emails from Shopify to go through, you can have that email provider whitelist the following:
Should this alone not work, you can also ask the said provider to ensure there are no other restrictions in place which would be blocking automated mails sent from our system.
All the best!
I am having this same issue. When I called Cox.net with the info. They said that Google holds Shopify's domains and Microsoft holds Shopify's email systems. He said that I have to contact Google or Microsoft to get this issue solved. I doubt either will be able to help us with this. He let me know that Cox was not blocking anything. So as the other Shopify merchant said "It isn't their problem."
Cox gave me a link mxtoolbox.com this is used to look up for email delivery problems but at this point I don't really know how to read it or what I am looking for. So we just need this solved because our list of people with Cox is growing and they are not able to receive any emails. ANY emails at all...