We run our main site off a subdomain and are getting emails (sent with sendmail) bounced with error: 554 IP name lookup failed. No PTR record found. It looks like the fix is to rename the droplet to the correct hostname. https://www.digitalocean.com/community/questions/dns https://www.digitalocean.com/community/questions/how-do-you-update-reverse-dns My question is whether my hostname should be site.com or prod.site.com, remember that people access prod.site.com. One of those links says mail.site.com.