there is no report. in BW.   You're most likely using Outlook to send the emails.

Check the SENT FOLDER - you can do a search on the folder; default subject "OE Invoice" or "AR Invoice"

to verify the actual "TO:" address(es)

In BW you can also create a report to see the AR email addresses, but remember that can be over ridden while "PRINTING" (EMAILing) the invoice. There maybe up to 3 email addresses in AR Customers ( finance, Purchasing, Ship to)

Also if you use Order Entry, there is a place for email address in "SHIP TO"

Currently there is not a report that shows if an invoice was emailed or what email address was used. By default it pulls the email address for Finance contact in Maintain Customers.