The Huddersfield-based business has been awarded a "long-term" contract to produce the charity's supporter communication collateral, which will comprise personalised mailers.
The contract was initially due to begin in the first quarter of 2011 but the transition from incumbent provider Mailcom took place earlier this month following Mailcom's administration in December 2010.
Adare is producing bespoke, targeted mailings for the wildlife charity aimed at retaining members and encouraging future activity by incentivising supporters.
The contract comes on the back of a recent £3m investment in new digital print and enclosing machines including dual InfoPrint 5000 digital print engines, two CMC hi-intelligence enclosing machines and two Jetstar postal sortation units.
Darren Flint, marketing procurement manager at RSPB said the time was right for the charity to communicate with supporters in "an ever more applicable and timely way".
"This means that we need to move away from standard messaging and instead issue highly personalised communications that are relevant to each of our individual supporters," he added.
Robert Whiteside chief executive at Adare, said: "Our continual investment in people, processes, equipment and technology has given us a robust and flexible platform from which we are able to support RSPB as their business requirements change".
Adare currently employs 700 staff across 30 locations in the UK and Europe. It has a turnover of around £135m and clients include HMRC, Whitbread and IBM.
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