[LeonM]

> You can’t

You can, but as long as the user owns the domain they are sending with.

If the domain owner authorizes you as a delegated sender using SPF and DKIM, then you can send email as [e-mail].

However, I recommend the OP learns about how email works before diving into such venture.

[tamimio]

If you own the domain you can pretty much do anything, from hosting your own email to having unlimited aliases, but I believe OP question is a bigger scope as said “personal emails”, so that also includes emails from other providers like gmail etc., so I stand corrected (if I understand OP requirement correctly anyway), you can’t unless you are spoofing it, which is useless as it will end up in the black list anyway.