Current email status labels are:

Open, Click, $0 Donation

I would like to suggest to update the status labels for email activity that is sent via NXT to have the following labels to make it less confusing:

Received, Open, Click, Transaction

Putting a $0 Donation as the email status is misleading, especially if the transaction is for an event registration that has no fees. And if it did have a fee, it is not a donation, but rather a 'Fee'.