When you set up a new account, your device usually displays only the most basic settings needed to connect, such as your email address and password, and it figures out—or makes educated guesses as to—the rest on its own. However, those guesses may not always be correct, or at least not to your liking. Fortunately, you can fine-tune quite a few things in Mail (if not quite as many as in a typical desktop email client).
Some of these settings apply to any account type, some depend on the protocol (POP, IMAP, or Exchange ActiveSync) used with a given account, and some vary based on the email provider you use.
Except as noted, you do the following to adjust any of these settings:
Go to Settings > Mail, Contacts, Calendars.