Home › HubSpot Inbound Certification Fill in the blank: A is an email that has been returned to the sender because the email address is invalid. By · Tuesday, January 24, 2017 Fill in the blank: A ______ is an email that has been returned to the sender because the email address is invalid. A) Hard bounce B) Soft bounce HubSpot Inbound Certification GA Gaurav Arora, Digital Media Lead. 10+ years running paid media and tracking for brands in the USA, UK and Canada.