Ask HN: How to anonymize/alias emails submitted in forms?

I have a form where the user enters an email on which they want to be contacted. However, I am not legally allowed to collect anything that could potentially identify the user.

I am looking for a solution that would automatically generate a random email alias on form submission, so that I would be replying to xyz123@aliasprovider.com and they'd receive it on their john.doe@ibm.com, without me ever seeing their real email address.

This should be a solution that works fully on client side (without need to install browser plugins or perform any action), maybe hits 3rd party API or mail server, and their address is impossible to retrieve on my side.

Thank you for any advice!