Inbox will initially be responsible for developing a new identity for Endsleigh Insurance's online and offline work, including a website refresh, and will later create an eCRM campaign aimed at forging a closer relationship with customers.
said the appointment was part of its push to become more digitally focused, and described online as its "primary pipeline" for business.
It is understood that Inbox's appointment will not affect Tamar's existing relationship with the insurance company.
Stuart Wartalski, head of corporate communications at Endsleigh, said: "Email communications have become a key method of contact with our markets.
"Inbox showed an intuitive understanding of the brief, combined with the capability to deliver on a sound digital strategy that will help us meet our objectives, from groundwork branding through to complex, data-driven eCRM solutions."