Sometimes when you start a new email message, iOS suggests an email address that's no longer being used, and has already been removed from your Contacts. How can you tell your iPhone, iPad or iPod touch to stop using that address when you enter a contact's name? Here are instructions on how to remove this old email address from the list.
First open the Mail app and start a new message. Start to enter the name of the contact. You will see a list of suggestions from contacts and the recently used email addresses.