It's possible that the email tracking feature was available in the software or service you were using. However, without knowing which specific software or service you were using, it's difficult to provide a precise answer.
In general, most email programs or services offer some form of tracking for sent emails. You can typically find this information by looking at the "Sent" or "Outbox" folder in your email program or service, and reviewing the details of the messages you've sent. Depending on the program or service, you may be able to see whether the message was delivered, opened, or clicked on.
If you are using an invoicing or accounting software, it's possible that the software has its own email tracking feature that allows you to see which emails were sent to your customers. You may need to consult the software's documentation or contact their support team for assistance in locating this feature.
