Yes, you can track the emails that are sent to your customers for their invoices, estimates and retainer invoices. The Email Insights feature in Zoho Books enables you to do so.
To enable Email Insights:
After doing this, Email Insights would be enabled in Zoho Books.
With Email Insights, you can view the time and date the emails (containing the transaction) that you send to your customers are opened by them. In the transactions list page, you can track the status of each email sent with the help of the following icons:
If you want to view transactions that have been viewed by your customers, you can also filter the transactions by the Client Viewed category from the transactions list page (through Client Portal or email).
Note:
If the email you sent has multiple recipients or has users’ email address in CC or BCC, the corresponding transaction will be marked as viewed when any one of them views it.