This is a great reason to ensure your mail client doesn’t auto-download embedded images, send read receipts, etc.
No reason to tip your hand until a lawyer tells you to. For instance, the last time I dealt with a lawyer, they had me send responses directly, in hopes the other side would underestimate our position. It worked, fwiw.
That's irrelevant for this issue. Domain holders have to provide working email addresses as a condition of registration, and are reminded annually to keep their addresses up to date.
If an email address can't be found, the correspondence can be delivered through other means if necessary (mail, process server, etc.). But generally, there has no longer been a need to waste paper and postage to deliver notices since email became practically ubiquitous.
IANAL but I am an internet plumber. Happy to provide expert witness that e.g. Hover, owned by Tucows, has a toggle for whois in their domain admin dashboard but it does nothing: I cannot turn whois on even if I want to.
Having, or publishing, an email address does not mean I care to, choose to, or will in fact receive email sent by you; or that I will display or treat it in the fashion you desire.
They may not check their email, but how is anyone on social media without email? I'm not aware of a single social site that doesn't require an email address to create an account.
