I absolutely always read rejection mails...although I haven't seen one in quite a while...knock on wood
Acceptance mails...unless the subject line lets me know there's something other than 'you're listed' in the mail...nope, don't usually read those.
Then, there are those sites that send out mails with an ambiguous subject line. Most of those are sites I know quite well and that have always listed my stuff. I still tend to spot check those for anything unusual.