@Paul_Haze It depends on your account with DreamIt. If you have a separate arrangement with them to host your e-mail, then you can use DreamIt, but you need to get their MX entries to make this work.
When you use an external e-mail service, you use that service for your e-mail, you don’t point your DNS at that service and then have that service point to some other service. The whole point of the MX records is to enable you to set up a direct connection from your SOA.
This whole discussion is academic, however, because you have now removed your site from Netlify hosting.