"I opened your envelope. Now what?"
You break the silence. Maybe ask a question. That's always a good start. "Did you ever wonder?" You're trying to turn on a conversation in the reader's mind. You start small. You start simple. You speak as you would speak to a good friend or a loved one.
You ask for a gift. Humbly.
You continue a story you started maybe on the envelope.
You pour shine on the power of donors to make a difference.
You ask again humbly.
You continue your story. Another fragmentary, vivid detail dragging the reader through the pain, awakening empathy in its trail.
You look them straight in the eye and you love them for who they are about to become and for who they really are, beneath the crust and the mistakes and the weariness.
You ask again.
You thank again.
Humbly.
You sign off wonderfully, surprisingly, delightfully.
Your PS (PPS, PPPS?) is/are a shooting star, searing the reader's night brain.
Your reply device extends the glow.
Your reply envelope extends the glow.
You call back soon!