Question for people familiar with Cases….

My understanding is that a new case coming in is assigned to a customer based on the sender email address. The business account/customer must have that email address in their record under Account Email (see below). This is of course assuming that the “Attach to Business Account...” setting is turned on in the system email account. 

My question is… what if there are multiple customers who share that email address? I tested this and it will assign the first instance of the email address, which may not be the correct customer. 

We are using Cases to create service orders, so we receive dispatch emails from vendor management systems that several of our customers use. So, the sender email is the same, but the customer might not be. 

Does anybody know how the system can figure out the right customer to assign the case to in this circumstance?