Wierd Issue with Outlook

So I have a user who is receiving (Regular - New order document) emails from a domain, but they're not receiving PW reset or User account confirmation emails from the Domain. 
All the emails come from the same Email address (IE: no-reply at domainname dot com) 

What's really interesting is I have had our IT Engineering team look into this and they say this person does not even receive Emails from the domain (even though they daily receive the new order document emails). 

Any idea why this would be happening?

I can't understand how they can be receiving the emails, yet our Email engineers say that Nothing is coming into the system for that users email address from the sender's email address.