Annotations are used to manage Gmail Promotions Tab markup. This markup allows for a condensed version of your email message to be bundled at the top of the promotions tab in the Gmail iOS and Android apps. For more information and higlights see the Gmail Promotions Tab Guides.
To get started click on your Tools tab and then select the Annotations option. From here you can mange previously made annotations and create new annotations.
For this example, we are going to click the Add Annotation button.
Once you've filled out all the fields you can click on the Save button to save the annotation. Once an annotation is saved you can insert the annotation on any mailing underneath the Advanced Options.
The annotation will appear on Gmail accounts using the Gmail iOS or Android app. A preview of what recipients will see is pictured below.