So it’s your first Christmas apart and you’ve decided to send your ex a card. The dilemma that now faces you, is what do you write inside and how do you sign off? “Best wishes,” sounds a little too distant; “regards,” is far too formal; “love from,” is just plainly inappropriate. Then if you can work out the correct sentiment do you put “xxx” after your name or not? Yes, you do write it on Aunt Ethel’s card but she is elderly and she is not your estranged spouse. Of course you could just write your name, after all the card itself will carry a printed message in any event; but a name by itself looks exactly that and you don’t want the ex thinking of you as all alone, one short name on a piece of paper.
Frankly the time spent agonising over “Do you, don’t you and if you do, how?” is not worth it. Far, far easier to pick up the phone and wish them a Merry Christmas verbally. If you are unable to communicate directly in that way then don’t send a card; it’s meaning is going to be misinterpreted and you may regret it later.