The move is part of a wider plan to develop closer relations with existing customers and attract new prospects through greater use of digital media.
InBox Digital, which was hired in November after a three-way pitch, will develop eCRM activity across a range of retail products, including loans, credit cards and mortgages.
It will be managed using Inbox's in-house management system, which supports eCRM activity for clients such as BMW, AOL and Vodafone. The system is capable of deploying dynamic content emails and provides real-time reporting.
Activity should include email marketing and will be targeted at a wide audience, with the aim of driving incremental revenue.
Inbox will work with Alliance & Leicester to identify core target customer groups.
The appointment rounded off a good year for Inbox, which recorded 60 per cent growth and gained several new clients, including Panasonic, The AA, Procter & Gamble and HBOS.