No, you don't need to write a letter. A phone call will suffice.
Her example alone should suffice to show that anything is possible.
She's also decided that she can't countenance her mother, who gives Jane cash but demands that her daughter save every receipt or package to prove that she didn't spend the money on drugs. Suffice it to say, their short-lived truce is over. —Alec Klein, A Class Apart: Prodigies, Pressure, and Passion Inside One of America's Best High Schools, 2007
Thirteen years later, I still don't know exactly what to make of this letter. It goes without saying that a simple thank-you note, especially nearly a year late, would have sufficed. —Scott Turow, Atlantic , December 2005
But what of the meteoroids that come from other large objects in the solar system? To escape from Venus or the Earth, matter must be ejected at a velocity of at least seven miles a second; on Mars, three miles a second will suffice. —Donald Goldsmith, Natural History, September 2003