Can I have Project members without an email address?

Can I have Project members without an email address?

I am planning a house construction project. Many of the involved companies will definitely not use Zoho or any other online tool but I want to mention/assign them in my plan nevertheless. It would be useful for this purpose to have users with onla a name (e.g. electrician) and no email address. Is this possible (or could it be made possible)?