So, I read The Skimm every day, and today they had this as the end note:
#X: If someone texts you that, it’s not a typo, a drug reference, or something involving porn. It’s a hashtag PSA that people use via text to let you know they’ll be radio silent while on the road. Ex: “Getting on the road #X” Don’t text them.
I can’t tell you how tempting it is to make “#X” my e-mail signature line. I’ve never had one. Maybe now is the time?