The ubiquitous custom of writing (or typing) "Xs" on the bottom of cards, notes and letters to indicate kisses dates back to those pesky Middle Ages, when the "X" represented a crucifix and signified sincerity, faith and honesty. A kiss placed upon the page signified a sworn oath to Jesus (in more modern terms it evolved into a sign-off, like sincerely or devotedly). The "X" was also accepted as a signature for those who could not write their name, but that's another story.
The "O" is a universal symbol for hug; a circle signifies the act of enveloping (a circle of life) and is a sign of endearment.
Some sources claim that in the late 19th century, the "O" was substituted for a cross by Yiddish-speaking Jewish immigrants to the U.S., and used when signing letters or documents.
Today, "XOXO" means hugs and kisses (or kisses and hugs, I can never get it straight). But beware, this otherwise harmless representation may be vulnerable to a new wave of woke scrutiny …
… as a target of the current damned-if-you-do-and-damned-if-you-don't sociocultural behavioral pandemic. Can we continue to use "XOXO" in North America as shorthand (or default) for affection on personal letters and cards? I'm not certain.
Even if hugs and kisses get through the dragnet, don't press your luck with "XOXOXOXO," which suggests even more intimacy. Definitely remove it from auto-sign. And you're walking on thin ice by adding a heart [e.g. I HEART u] to the symbolic litmus test. The more emoticons and emojis there are, the greater likelihood of being policed for making an innocent mistake. Although hearts are usually harmless, you never can tell what alarms they might trigger. Unwanted hugs and kisses icons could sound hair-trigger alarms. Neutrality is the safest course of action (a simple period won't offend anyone … or will it?). So rather than get trapped by the stigma-enigma, it is always safer to not use "XOXO" in letters, emails or memos without prior approval of the recipient. For that matter, stay away from "XXXX" or "XXX" or "XX." I think you can get away with "X," but maybe not.
Absurd as it seems, this might just be a logical extension of sensitivity policing. Or is it?