So I've played STO pretty consistently from the start. But I just took a new character through the tutorial, and got an email about it, telling me basic stuff about the game and trying to get me to buy stuff. Does this happen on every new character from now on, or am I good now that I've taken a character through the tutorial once since this feature has been added?
Because it would be SUPER annoying if I got an email every time I took a character through the tutorial.
I assume it does automatically send you one. It may not if you decide to skip the tutorial (that being an option after you've completed it once). Although you'll be hearing from them again at level 10 iirc.
If you uncheck the option in your account management settings regarding them sending you mail, it will likely stop.
This is one of the policies brought over from when the PWE transition happened. In most of PWE's games, when you hit a certain level or get in the range of a quest hub, they'll email you about new things you can do in their games at your toon's levels.