While you can’t officially change your alias email to your primary email in iCloud Mail, there is a workaround that allows you to only send messages from one of them. Here, I will show you how to convert an alias email to your primary email on web, Mac, and iPhone.
Mac
To change your alias email settings from a Mac, you need to go to the iCloud Mail website. I couldn’t find any settings to do this in the native Apple Mail app, so this is by far the easiest option.
To convert your alias email to your primary one on the web, you’ll first need to navigate to the iCloud Mail website. When you’re here, enter your login details. Depending on your account settings, you might need to verify your login attempt via two-factor authentication (2FA).

Navigate to Mailboxes -> Settings.

Scroll down to Send From and tap the horizontal three-dot icon.

Expand the Default Send Address dropdown menu and choose your alias email. Then, untick your “primary” email so that messages are only sent from your alias.

Select Save Changes once you’ve adjusted everything you needed to.
iPhone
Although you still cannot add alias emails from your iPhone, you can at least change your settings to send emails from your alias address. First, you’ll need to go to Settings -> Apps.

Navigate to Mail from the dropdown menu when the next screen loads.

At the top, select the Mail Accounts tab.

Go to iCloud.

Select Default Email.

When the next window appears, choose your alias email address. All messages you send will now primarily go from this address instead of your old main account.
What Happens if I Convert My Alias Email to My Primary Email?
Since you can’t explicitly turn an alias email into your primary one, not a huge amount will change when you change your settings. The main thing you’ll notice is that you’ll now send emails from your alias account. Depending on your settings, you may still also send messages from your original primary email address.
You can easily reverse the changes you made to your settings. To do so, you simply have to go back into your iCloud Mail settings on the website or your iPhone. Here, follow the same instructions you did to send emails from your alias (but in reverse).
Another important thing to remember is that you won’t lose access to accounts where the primary username is used (including iCloud storage). This is because it’ll still be your official account address, despite sending emails from your alias. Because of this, your iCloud login details will remain the same.
Once you’ve changed your alias email settings, you can still add your iCloud email to Outlook and other services that you use. So, you should have no problems using your emails like normal.
Changing your alias email in iCloud Mail isn’t fully possible, and as such, I don’t think that doing so will make a huge difference in how you send emails. You should only do it if you want to organize your emails more effectively. When doing so, you might also want to check out some of the Apple Mail alternatives available for Mac.
Image credit: DALL-E. All screenshots by Danny Maiorca.
