Even inside a spoiler box, the text will still be readable in an email.
If you can’t see an episode, it’s important to cancel your subscription to a thread. I can’t say how many times I’ve gotten inadvertently spoiled via the emailed text. 
Also, please, if you see something that should be in spoiler tags, report it… but, please, please, please, don’t quote it. When you quote the spoiler, it just doubles the work the moderator has to do to clean up.
Aw, man, I’m sorry, guys.