N=1, but my small email server actually hosts emails for a business, and the only problems I've ever had were with Microsoft, and they went away after i jumped

N=1, but my small email server actually hosts emails for a business, and the only problems I've ever had were with Microsoft, and they went away after i jumped through some hoops for them. I'm using a linode and dkim/spf/dmarc/tls/rdns.