This guide will help you to setup Topmail on your iPhone 6 (iOS version 9.3.2) using a step by step process. If you only need the server settings information for Topmail you can get that here: Topmail Server Settings
Open your settings App. Scroll down to the "Mail, Contacts, Calendars"
Tap on "Mail, Contacts, Calendars"
Tap on "Add Account"
Tap on "Other"
Tap on "Add Mail Account"
Enter your name (eg. Your Name), full @topmail email address,
your passphrase (password) and description (eg. "Topmail").
Tap "Next"
Select "IMAP" as the account type.
Enter the following settings for the incoming mail server:
Host Name: imap.topmail.com
User Name: your full @topmail.com email address
Password: your @topmail passphrase (password)
Enter the following settings for the outgoing mail server:
Host Name: smtp.topmail.com
User Name: your full @topmail.com email address
Password: your @topmail passphrase (password)
Tap "Next"
Select your notification preferences.
Tap "Save"