The e-mail address for the validation can’t be chosen at will.
The CAB Forum (Certificate Authority and Browser Forum) has determined that only domain-specific e-mail addresses are permitted for validation in order to occupy access to the domain.
Examples are among others:
Alternatively, an e-mail address from the WHOIS (NIC) can also be used.
In this way, the certifiers want to ensure that only those individuals /companies receive SSL/TLS certificates that are actually authorized to do so or have received permission to do so from third parties.