You cant send mail from Hide My Email aliases. They are only work one way.
You can send from Hide My Email addresses:
https://support.apple.com/guide/icloud/use-hide-my-email-in-...
I think I've also seen this in Mail.app but that's not shown on this page.
alt Hacker News
You can send from Hide My Email addresses:
https://support.apple.com/guide/icloud/use-hide-my-email-in-...
I think I've also seen this in Mail.app but that's not shown on this page.