That account requires an email address for whatever.

ICANN regulations require registrars to collect email addresses, and that apply to gTLDs, but ccTLDs have often similar constraints, so that the registrars and the registry can contact end client in case of problems.

With the current legal frameworks (GDPR and the like), it is often hidden in whois output, but not always. Do a whois on apple.com and you will see what email address they used.

Nothing special there, anyone is free to use any email they want.

Also big companies, and for example for hidden/not announced project, often used proxies to register names, like attorneys or their registrar acting on their behalf.

What specifically triggered your question of

If this is true, what email do large companies/corporations use to buy their domain name?

Anything particular in mind?

That account requires an email address for whatever.

ICANN regulations require registrars to collect email addresses, and that apply to gTLDs, but ccTLDs have often similar constraints, so that the registrars and the registry can contact end client in case of problems.

With the current legal frameworks (GDPR and the like), it is often hidden in whois output, but not always. Do a whois on apple.com and you will see what email address they used.

Nothing special there, anyone is free to use any email they want.

Also big companies, and for example for hidden/not announced project, often used proxies to register names, like attorneys or their registrar acting on their behalf.

What specifically triggered your question of

If this is true, what email do large companies/corporations use to buy their domain name?

Anything particular in mind?

So you edited the question later to add:

The question is what email do corporations use before they even have a domain name?

Yes, of course, if you buy example.com, it is not possible to use email address [email protected] in advance, before the domain exists (possible to use if no checking tool verifies the domain name existence in advance, but even so, obviously no emails can be received there so if you need some email validation thing going on, you're blocked).

More complicated than that as you might be conflating two separate issues:

• to create a domain through some registrar, you need an account; creating an account needs an email address generally (but that remains specific to any registrar process)
• when you create a domain, you chose contacts, which have email addresses and those email addresses may appear in public whois/RDAP queries, or not, but anyway can be (should be I would even say) completely different from the email address used by the account owning those names at that specific registrar.

Sometimes the contacts email address are just that, and have no power on the name itself. Other times, and in the past, there were options like "send authcode to admin email address" or "reset account password and send link to registrant email address". All of that is specific per registrar and their security processes and posture.

But even so, it is often not recommended. Or more precisely it is complicated:

• if you register names with specific other email addresses then the security of your domain might be in fact tied to the security of those email addresses if anything related to domain account management can go through those email addresses (even worth, and a known "attack", if the domain name on which those email addresses are is expiring and is registered by another party unbeknownst to you...)
• if you register names with email addresses in those names (easy: you register with other email addresses and you later change them, which is why a whois query on apple.com shows email addresses of [email protected] and the like), you are then vulnerable to any problem affecting this domain resolution, as it might mean nothing will work for it anymore... including the email addresses under it.

Hence the choice between those two cases is not easy, and they need at least to be clearly seen.