Edit the SITE123 Mailbox on iPhone
To set up your email account on your iPhone, follow these steps:
On your homepage, look for Settings
Scroll to Passwords & Accounts.
Click Add Account
Click Add Mail Account
Enter your email details and click Next
Under Incoming Mail Server and Outgoing Mail Server, set the Host Name to mail.enter-system.com and add your email account details.
After submitting the details, the iPhone will add your email to the accounts list.