Select the settings icon on your home screen
Select Passwords & Accounts
Select Add Account
Select Other from the menu
Select Add Mail Account
Enter your account information
Enter your Name, Email & Password > Next
Configure Incoming and Outgoing Servers
Select IMAP (default) or POP according to your needs (See POP vs IMAP)
Scroll down to Incoming Mail Server and enter all the relevant details, then do the same for Outgoing Mail Server, as in the screen below and then select Next.
Incoming mail server: has mail. before the domain name e.g. mail.example.com*
Outgoing mail server: has smtp. before the domain name e.g. smtp.example.com*
Ensure that User Name is the full email address
User Name & Password are the same for both Incoming & Outgoing servers
You have completed your account setup.
Congratulations! You have now successfully configured your email account on your iPhone.