It would be useful to rename the Field names Email1 Email 2 Email 3 etc to something useful at a global level, so when sending documents by email we know which email address to pick from against each document type allowing conformity accross the system
For Example
Customer Email1 could be named "Sales Invoices"
Customer Email2 could be named "Statements"
Customer Email3 could be named "Order Acknowelgments
Supplier Email1 could be named "Purchase orders"
Supplier Email2 could be named "Remittance advice" etc
These names should be determinable by the company and then have conformity for all suppliers/customers with ease