my Iphone 6 sends an email multiple times

Try resetting your Mail Account.

First close your Mail App completely from the app switcher window by double clicking the Home button and swiping up the Mail preview pane up until it disappears from the screen. You may have to look for the Mail pane by scrawling to the left.

Then go to Settings > Mail, Contacts, Calendars > locate your email provider and click on the account. On the next page Delete Account.

Then do a forced restart. Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears.

Then go back to Settings > Mail… and add the account again.

You should be able to go to Settings > Mail, Contacts, Calendars > and click on Add Account. Just follow the prompts from there.

Add an email account to your iPhone, iPad, or iPod touch - Apple Support