Email plays an important role in the digital economy but is threatened by increasingly sophisticated cybercrimes. A number of security services have been developed, including an email authentication service designed to cope with email threats. It remains unknown how users perceive and evaluate these security services and consequently form their adoption intention. Drawing on the Technology Acceptance Model and Technology Threat Avoidance Theory, this paper investigates the factors that affect user intention to adopt an email authentication service. Our results show that user intention to adopt an email security service is contingent upon users' perception of risk and evaluation of both internal and external coping strategies. This study contributes to research in security service adoption, service success and design, and information security behaviour.