Email not sending updates

We recently paid for a site rebuild and email was not reaching our domain so the developer created a forwarder as a work around that allowed customer emails to get to us. This however should have been a warning sign, Administrative emails aren’t getting to me. What is the simplest and best method for fixing the email settings (likely SMTP) so I can get updates from the site?

I’m open to plugins but a bit reluctant as WP is new to me.

Thanks,