Thx

One writes “thx” if one wants to show an amount of gratitude, but only a small one: not so generous that it warrants being bothered to type all six letters of the word “thanks”, or even setting up an autocorrect so Microsoft can do it for you. If co-ordinated with a generously populated cc: line in a reply-all mail, it has the potential to vaguely irritate a lot of busy people at once.

Often used when adding.