Any document emailed in Tally is recorded as a note at the bottom of the page, this contains the date that the document was sent and also the send-to email address.
To find out if an invoice has been e-mailed, just go to Sales > Select your invoice > Scroll to the bottom and view the Notes Section.
Remittance Advice, Quotes & Purchase Orders
This process also applies to emailed remittance advice, quotes and suppliers emailed purchase orders.
Customer & Supplier Statements
Emailed customer statements can be accessed by clicking Customers > Selecting the customer > Click Notes & Files. The date of the statement being sent is displayed under the notes section. Supplier statements are visible in the same way by going to Suppliers > Selecting the supplier > Clicking Notes & Files.