Wireless
Why this works:
Push mail is one of the biggest reasons why your iPhone battery drains fast. When your mail is set to push rather than fetch, your email server will be constantly connected to your iPhone so that you can receive emails as soon as they arrive in your inbox.
When you switch to fetch, your iPhone will connect to your email server every certain number of minutes (we’ll recommend every 30 minutes) and check if there is any new mail.
Changing mail from push to fetch means you may have to wait a little while longer before being notified about a new email in your inbox, but it will do a lot to extend your iPhone’s battery life in the long run.
Pro tip: