I think I need a DNS technician

I have a website that is set up to automatically send email notices to subscribers when I do a post. Many subscribers don't get the notice. I was referred to WPMail to help me with this problem, and I subscribed to them. They have referred me to Sendinblue, which has devised DNS files that have to be added into my dns zone on my web host, A Small Orange. I haven't figured out how to do that. ( I'm not a technical person--I don't even know if I'm explaining this correctly.) I would like to hire someone who can look at my e-mails with Sendinblue and do what I need to do..I suspect that someone who understands this stuff can fix it pretty quickly, but it's a nightmare for me.