My company has changed the owner of the [same] domain name,  and set it up with a new website's host and server. I've realized that currently all email can't be sent out. We have 19 email addresses. My guess is that I need to point new IP or the nameserver to this same domain name. So how can I do that?

The new host is hostatom.com and my domain is registered with thdomain.thnic.co.th