In case the automatic setup fails, here is the manual setup on an iPhone / iPad:

Open Settings.

Tap Accounts & Passwords.

Tap Add Account.

Tap Other.

Tap Add Mail Account

Enter your name, email address, password, and a description for your account.

Tap Next.

If Mail finds your email settings, tap Done to complete your account setup.

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If Mail can’t find your email settings, then you need to enter them manually.

Tap Next, then follow these steps:

Choose IMAP or POP for your new account, depending on your needs.

Incoming mail server
Host name: your_domain.com
User Name: Enter your full email address
Password: Enter your email password

Outgoing mail server
Host name: your_domain.com
User Name: Enter your full email address
Password: Enter your email password

Tap Save.