Jay, I’ve also tried that, perhaps my attempt to make an MX record is inaccurate .. I get and OK config at Mxtoolboxdotcom: (no PTR record, no support for TLS, otherwise all green)
We have to have a DNS record that directs our TLD email to our outgoing mail server, that seems to override my attempt to send mail to the server / subdomain, viz: sending test email to nobody@discourse.TLD,domain shows up in the mail receiver logs as:
reject: RCPT from outgoinghost.otherdomain 454 4.7.1 <nobody@TLD,domain>: Relay access denied; from=ME@otherdomain to=nobody@TLD.domain
I have this MX record:
MX Record HOST discourse.TLD,domain VALUE discourse.TLD,domain. PRIORITY 10 TTL 1 min