Some services, like Facebook, normalize the mail address (turn all letters to lower case). Can you make sure that mails to the normalized email also reach my inbox? (They don't now!)
What provider doesn't violate that part of the spec? I see plenty of sites/services that uppercase my email address for whatever clever reason they feel is necessary; not violating that part of the spec and actually making the address case-sensitive would be a detriment to the users.