Clarifying AAD email address attribute prereq

Adding another sentence for the AAD email address attribute description, just in case admins forget to set up mailboxes that match the attribute they select here (failure to note this caused some internal test cases to be incomplete and fail). Adding this to all platforms.

Author: tycastMSFT

memdocs/intune/configuration/email-settings-android.md

@@ -56,7 +56,7 @@ Create an [Android device administrator Email device configuration profile](emai
       When choosing to use **Custom** attributes, enter:
       - **Custom domain name to use**: Enter a value that Intune uses for the domain name, such as `contoso.com` or `contoso`.
 
-- **Email address attribute from AAD**: This name is the email attribute Intune gets from Azure AD. Intune dynamically generates the email address that's used by this profile. Your options:
+- **Email address attribute from AAD**: This name is the email attribute Intune gets from Azure AD. Intune dynamically generates the email address that's used by this profile. Make sure your users have email addresses that match the attribute you select here. Your options:
   - **User principal name**: Uses the full principal name, such as `[email protected]` or `user1`, as the email address.
   - **Primary SMTP address**: Uses the primary SMTP address, such as `[email protected]`, to sign in to Exchange.