The daily notification emails are sent out Monday to Friday at 7:30 AM PST.
The daily notifications include:
A count of Invoices, POs, and Payments owned by the recipient on the In-Progress tab
A count of Invoices, POs, and Payments pending the recipient's approval
A summary of new comments left on Invoices, POs, and Payments owned by the recipient.
In addition, we have a concept of "Urgent Invoices" and "Urgent Payments", which means that the email title will be aggressive, and certain items will have special attention brought to them.
An Urgent Payment is a payment which is due in 48 hours or fewer
An Urgent Invoice can be set thresholds for being older than X days after received date or having Y days or fewer until the due date.
For instructions on how to enable Notification emails, please see this article.