I wanted to do the same thing, to test their email address. Did you get a reply yet? Generally, it does not take much time to get a response from the server if the address is not correct.
They have another address on the website, has it been checked as well?
I was checking some email validators, and the response is positive from the servers. Apparently they use the protonmail.ch service.
Now, they may receive emails and not respond for some reason.
And has anyone tried talking via Telegram?