Salesflare connects a lot of information automatically to a contact based on his/her email address. This level of automation makes it very difficult to allow editing the email address.

If the email address of a contact is wrong, just delete the contact and create a new one with the correct email address.

If you have multiple email addresses for the same contact, it's best to create multiple contacts (one per email address) and optionally connect all these contacts to the same account to see all communication in one place.