Virgin Media was the only brand to pick up two awards at the ceremony held at Kensington Roof Gardens, which were for Best Designed Magazine (consumer) and Best Overall Creative Solution.
Electric, published by Redwood, is mailed to customers to ensure that key messages reach the company's entire customer base and is designed to enhance the Virgin Media customer experience and educate people about the extra products available.
The judges were impressed with the magazine's "stylish blending" of editorial content with information on the client's services and felt that its "ability to change perception is its greatest quality".
Other winners included British Heart Foundation for Best Creative Innovation Online, The Goodwood Revival Programme for Best Creative Use of Print, Royal Mail Contract for Best Designed Magazine (B2B), Duchy Originals for Best Designed Website and Audi Magazine for Best Front Cover.
Julia Hutchison, chief operating officer at the APA, said: "Over the last year the customer publishing industry has experienced an explosion of creativity and the competition in each award category was extremely fierce.
"This year we saw a 50% increase in the number of entries, building on the enthusiasm for the awards of last year."
Emily Fovargue, head of publishing at Royal Mail, said: "The creative bar has yet again been raised by the customer publishing industry and these awards reinforce the importance of the medium as part of a successful and powerful marketing strategy for major brands."