Notification Doctype - Recipients - Receiver By Document Field is not showing email field

In the above image, I selected the donation doctype, It has an email field in that doctype but it only shows the owner on Receiver By Document Field , it doesn’t show the email field how to fix this ?

It’s showing when the Option is Email, for example:

Please check the example of contact doctype.

Thanks Now its working fine

It works when the channel is set to email. But fot System Notification, it only shows the owner on Receiver By Document Field.
It is possible to set the recipient to other user besides owner? I tried when the option is user, and did’t shows. @NCP