I subscribed to sparkpeople.com with an address that had a ‘+’ in it.
Everytime I tried to unsubscribe, I got a “bad code or email” error.
I thought they were spamming me, but when I changed the “+” in the
unsubscribe URL to ‘%2B’, I unsubscribed fine (the “+” is
URL-translated to a space, and %2B is translated to “+”).