Mothercare aims to establish a comprehensive email programme for the business following its purchase of the Early Learning Centre last year.
Initially Inbox will develop a co-branded e-newsletter programme targeting parents in the key stages of their child's development with the aim of building brand engagement, driving response rates and ultimately increasing propensity to buy.
Data insight and planning will be handled by Inbox's digital marketing group partner Jaywing.
The agency will then work on acquisition campaigns aimed at increasing the data richness of existing email records and moving customers signed up to special offers to other email communications.
Alexa Proctor, direct marketing manager for Mothercare, said: "Although Mothercare and ELC have existing successful email programmes, we now need to build on that success to make email work harder for the business.
"Inbox showed a real empathy with the brands and our objectives for the programme, bringing to the table some great strategic ideas underpinned by top-notch creative."
Inbox specialises in digital customer relationship management and its clients include Procter & Gamble, United Biscuits, Vodafone, BMW, AOL, Alliance & Leicester and Fat Face.