You should be able to see the email on the account by adding it to the Mail app on your Mac, or logging into the account via http://www.icloud.com
In terms of changing an iTunes account's primary email address : Change your Apple ID :
You can change your Apple ID to any other email address you control, as long as it's not already in use as an Apple ID. If your email address ends with @icloud.com, @me.com, or @mac.com, it's already an Apple ID.
Apple Design Award Email. Airmail 3 — This fully accessible mail client was designed specifically for iOS, macOS and watchOS. Email workflow is optimized with extensive customizations, custom actions and deep integration with a wide range of apps and services. Discuss email privately. Invite teammates to discuss specific email and threads. Ask questions, get answers, and keep everyone in the loop. The new Spark feels like the first product that may finally solve email communication and assignments for the MacStories team.
So I don't think that you will be able to change it
Dec 13, 2014 1:36 PM
Add as many email accounts of any type your like to Airmail. (Gmail, GSuite, iCloud Mail, Exchange, Office 365, Microsoft Outlook, IMAP and POP3).
When you just want to see the important emails, the smart inbox is here for you. It automatically filters out newsletters and other distractions, leaving you with just the crucial messages.
When you don't want to deal with an email now, but don't want it in your inbox either, use the snooze function to hide it until it's relevant. From concert tickets to flight confirmations, keep the emails out of the way until you need them.
See all of the email in all of your inboxes at once with the unified inbox feature. You can even exclude accounts from this view if you want to.
If privacy is paramount then you can enable privacy mode which will process all the data locally on your device. Privacy mode also blocks tracking pixels, and prevents images from loading automatically.
Schedule emails for the perfect moment. Schedule your emails to land in the recipient’s inbox at just the right time. Whether it’s a client in Australia or a business partner in Europe, your email will always be on top.