I read many post regarding sent mail with the content of Lookup field.
The notification email doesn't show the content of Lookup field, instead, it shows the ID number.
Anup has answered for one post as following
In the new app builder interface the lookups by default is linked to the ID field. So when you set an email notification to get the exact data from the lookup field, you can set the field value as "input.Lookup_field_name.Field_name".
This way works well in setting FORM Email Notification
however when I want to sent email by FIELD Action - On Users Input - Sent Mails,
it always displayed Personality variable XX is not declared.