Google+ social network

Did you bother to read the exceptions?

Exceptions:

• You can't change the email address on your account to an existing Gmail address; however, you can add a new Gmail address to your Google Account.
  
• You can't change the email address on your account to an email address that's already associated with a Google Account.
  
• If you want to make your alternative email address the new primary address, first delete your alternative email address from the account.
  
• The new primary email address that you choose must have an active, valid email inbox that you can access.