Hi Bevula,

You can use the Audit history to view the customer email address and other details like  if an invoice was sent. 

Here's how:

1. Open the invoice.
2. Click More at the bottom.
3. Choose Audit history.

If you wanted to get a copy of your emailed invoices, you can add your email on the Blind Copy (Bcc) new invoices to address option on your settings.

Let me guide you how:

1. Click the Gear icon.
2. Choose Account and Settings.
3. Go to the Sales tab.
4. Click the Messages section to expand the preferences.
5. Under Sales form, choose Invoice and other sales forms.
6. Enter your email in the Blind Copy (Bcc) new invoices to address field.
7. Click Save then Done.

That's it! You should be able to view the invoice information. 

Let me know if you have any more questions. I'm here to make sure you are all set.