The YWCA, formerly known as the Young Women's Christian Association, launched the cold mail campaign in June in a bid to make a 25 per cent increase on any previous mail activity it had run.
The final results proved to be 10 per cent higher than the charity's target, with male donors outperforming women.
The test campaign, which was the YWCA's most successful for five years, asked for a £10 gift in the form of a letter, which was accompanied by a leaflet, a reply form and an envelope.
The response from male donors was an unexpected boost since its core audience is female.
Following the test, the YWCA is preparing to roll out a further mailing in October, which is a slightly tweaked version of the test campaign but with an increased gift request.
Joanna Matthews, fundraising director at YWCA, said: "The October mailing will test various gift levels, cold committed giving and, in the light of the results from the last mailing, whether gender really does make a difference or whether it was just a blip in the figures."
The new mailing features the YWCA's Maze Marigold project in east London that supports girls and young women involved in street sex work. It asks potential donors to help vulnerable young women escape life on the streets.
The test mailing was created by design agency Blue Frog and printed and mailed by Catalyst.
Following the test, Catalyst has been hired by the charity to carry out future marketing programmes.
Based in Oxford, the organisation works with young women aged 11-30 and runs a network of youth and community groups in 20 areas across England and Wales, supporting those affected by poverty, unemployment, violence and other forms of abuse.