Keep list of each date invoice is emailed

[sharonb]

When I email a customer their invoice, the date sent is listed. However, if I have to email it a 2nd or 3rd time, the new date overwrites the previous date & there is only one date listed. I would like to see how many times I had to email the invoice. I am wondering if there is a way to keep a list of each date that the invoice is emailed rather than replace with the latest date. I would like to be able to tell the customer each date the invoice was emailed whether it would be 1, 2 or 3 times. Thanks