When Acterra, an environmental charity in California’s Silicon Valley, recently revised its standard letter to thank donors, it decided to reinforce donors’ emotional ties to the cause, says Amber Nixon, the group’s development director.

Taking some advice from the free electronic book Lifetime Donor Attraction System, by the fund-raising consultant Pamela Grow, Ms. Nixon said she changed the first paragraph of the group’s letter to give the donor a “sense of joy,” included a personal story, and acknowledged each donor’s commitment to the cause.

Previously, each donor received the same form letter. Now it sends different messages for first-time donors, repeat supporters, and people who make big gifts.

Ms. Nixon said she also seized on a missed opportunity with the letter’s P.S. line, which asked donors to visit the organization’s Web site. Now that line asks donors to become a fan of Acterra on Facebook.

“It’s a better springboard for our relationship in the coming months,” said Ms. Nixon. “This will keep rewarding them.”

Below, see the organization’s original letter and the front and back of the revised message.

This letter is part of the Great Acknowledgment Swap, a collection of letters collected by Lynne Wester, director of stewardship and donor recognition at Yeshiva University and blogger at donorrelationsguru.com. You can see the full 638-page collection on her site.

As always, we invite you to critique the letters and borrow ideas for your own acknowledgments.