A line to record the event can be hacked into the email sending code fragment  - a sort of email log.

Thanks for responding.

under sales=>customer transaction inquiry=>view sales invoice, I find an invoice date and a due date, but no indication that the invoice was sent by email.  Maybe I am not looking in the right spot...

Normally I record this information in my job tracking software, but it recently happened that I was checking on an overdue invoice, and I didn't record if an invoice got sent or not.  So I have to assume I didn't send it, rather than knowing if it was sent or not.

It also happens once in a while where I would like to be able to say to a customer an invoice was sent on this date, then this date, then this date.  Thankfully I have very few customers where this is necessary, but it is good to have some evidence that I did my part when dealing with the one or two who need it...

So it would be a useful feature, I think...