To add a StarterMail email account into your iPhone's "Mail" app:

1. Open the "Settings" app » "Accounts & Passwords" » Add Account » "Other" » Add Mail Account
   
   
2. Enter the name, full user@domain.com email, password, and a short description.  Click "Next".
   
   
3. Assuming you're using IMAP, stay on this tab.  For the "Incoming Mail Server", enter

   Host Name	156.unihost.it
   User Name	user@example.com

   and your password.
   
   
4. For "Outgoing Mail Server", use the exact same settings you used for the Incoming Mail Server (hostname, username password).  Note the outgoing password is not optional, you must enter it.
   
   
5. On the next page, ensure "Mail" is enabled, and click "Save".
   
   
6. It's important to confirm the SSL options are enabled.  On the "Accounts & Password" page, click your user@example.com account.  It might only show your description, with "Mail" underneath, depending on what you typed.  Then click the "Account: user@example.com"
   
   
7. First we'll confirm SSL for SMTP in the "Outgoing Mail Server" section, click "SMTP user@example.com" » primary server: 156.unihost.it.
   Once viewing the detailed smtp server settings, ensure the

   Use SSL: ON

   is enabled.
   The "Authenticaiton" setting should be set to "Password", and the Server Port set to 587.
   
   
8. Next we'll confirm the IMAP settings, so go back so you're viewing the "Account" page, and at the bottom, there is a link by itself called "Advanced", click it.
   
   
9. Inside the "Advanced" page, scroll down until you see the "Incoming Settings".  We want to see:
   
   

   Use SSL	ON
   Authentication	Password
   IMAP Path Prefix	/
   Server Port	993