First, you are using Cloudflare for your DNS for Netsons.com, which is often not the best arrangement. You are, however, using Netlify DNS for gershomcharig.com, hence the error message.
Second, your mail server for netsons.com is shown as mail.netsons.com. Because you are hosting on Netlify, and Netlify does not run mail servers, you have a pointer to a mail server that does not exist. Your mail server for gershomcharig.com is undefined, so that’s never going to work.
You have a couple of options.
Easy: Change the a href mailto: links on your site to a working e-mail address (on a service such as Protonmail, Gmail, Yahoo, AOL, etc.) instead of e-mail addresses that use your custom domain names.
Harder: Set up e-mail forwarding to a known working e-mail address via ImprovMX. People will be able to reach you at e-mail addresses that use your custom domain name, but return e-mail from you to them will show your actual e-mail address. You will need to add a couple of DNS entries to get this working.
More difficult: Set up e-mail hosting for your custom domains via Gmail, Protonmail, etc., or purchase a separate hosting account with RackSpace, NameCheap, etc. (there are many others but the names escape me right now), and make the necessary DNS changes to integrate them into your situation.