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Massive X data leak affects over 200 million users.
(www.techzine.eu)
This is a most excellent place for technology news and articles.
When you get an email from Company A that sends to your alias email, the email goes to your inbox. When you reply to that email, your alias provider forwards it to Company A where the sender is your alias address.
In short, you simply reply and your alias service takes care of it for you so that the recipient only sees your alias email and not your true email.