You cant send mail from Hide My Email aliases. They are only work one way.

You can send from Hide My Email addresses:

I think I've also seen this in Mail.app but that's not shown on this page.

	▲	SXX 5 hours ago \| parent [-]
		Wow my bad I wasnt aware its possible. I remember someone in HN comments complaining about it being one way only back in 2024. UPD: apperently this supposedly only work if someone message you first. So you still cant spam from aliases.