The update email functionality allows you to create new product updates emails or send a previously saved product update email to your product updates subscribers.
Product updates emails are send to product updates subscribers only.
The create a new product updates email section:

Click on the “Create New Product Updates Email” button to open the product updates email details page.
The resume previous emails section:

The resume previous product updates email section lists all previously saved product updates emails and allows you to resume a draft or a previously started email. It shows details about the internal email ID, the subject of your product updates email, an abbreviated overview of the main content and the last save date of the product updates draft.