The initiative was launched this year to promote the responsible use of paper by demonstrating that the product is sustainable.
NAMMU head judge and chairman of SBS Business Solutions, Tony Keenan, said: "This industry leader helps ensure our creative livelihood in print is not only environmentally friendly, but also welcomed and recognised by our customers as such."
The NAMMU Environmental Awards are given to companies that help make the mailing industry as environmentally friendly as possible.
Lewis Fix, Domtar vice president of brand management and sustainable product development, said the campaign "showcases the utility and effectiveness of paper".
He said: "As part of the campaign launch, the Rainforest Alliance said that Domtar has raised the bar for the paper industry when it comes to increasing the supply of fiber from responsibly managed forests."
He said the company will continue to promote its FSC-certified range of grades during 2011.
Domtar's business papers are available in the UK through the Howard Smith Paper Group and Office Depot.