So, I just bought a used iPhone 4 and when I try turning on iMessage it asks for the email password of the person I bought it from. I signed into the app store using my apple ID but i still can't sign into iMessage. What do I do?
Check the email for the address you just logged into. You will have an email there with a link to go to to 'validate' or verify that email address then it should work. I just did this not 20 minutes ago on my own phone.