https://www.hallmark.com/card/about-sign-and-send

Offer open only to members of Hallmark's Crown Rewards program (membership is free). Sign in or create an account to send your first card free with Sign & Send! Must be signed in and linked to your Hallmark.com account to get offer. Valid while supplies last. In the Sign & Send program, you choose a card from the selection available, and you enter the US mailing address for your intended recipient. You then either

(1) type your message which Hallmark will print on the card,
or
(2) upload a pic of your message in your own handwriting which Hallmark will print on the card.

Then Hallmark will mail the card directly to your intended recipient.

Limit one free Sign & Send card per Crown Rewards membership. The card and the postage are free, and there is no sales tax. Not valid on past purchases. Consumer: Must be logged in to your Crown Rewards account at checkout and online promo code SIGNANDSEND must be used. Offer valid 2/28/21–12/31/21 only at Hallmark.com and only for Sign & Send eligible greeting cards. Hallmark.com orders require U.S. billing and mailing addresses.