If your iOS Mail settings default to an account you never use, you may change it to your preferred email account by configuring and changing the default. Here's how to do it:

1. Go to the Settings tab.
2. Tap Accounts & Passwords, then the name of your email account.
3. Go to Account and choose it.
4. Select Email from the menu.
5. Select an email address to use as the default by tapping it. As a result, you're From address in new emails will be changed to the new email account.
6. Select Address. If there is only one address listed in this area, you're fine to go

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