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-windows-10.md

@@ -60,7 +60,7 @@ Create a [Windows 10/11 Email device configuration profile](email-settings-confi
       When using **Custom** attributes, also 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**: Intune gets this attribute from Azure Active Directory (AAD). Choose how the email address for the user is generated. Your options:
+- **Email address attribute from AAD**: Intune gets this attribute from Azure Active Directory (AAD). Choose how the email address for the user is generated. Make sure your users have email addresses that match the attribute you select here. Your options:
   - **User principal name**: Uses the full principal name as the email address, such as `[email protected]` or `user1`.
   - **Primary SMTP address**: Uses the primary SMTP address to sign in to Exchange, such as `[email protected]`.