Please see https://docs.cloudron.io/email/#server-status . Specifically https://docs.cloudron.io/email/#ptr-record and https://docs.cloudron.io/email/#outbound-smtp
There it is !
it worked! Created a Type A DNS record for my.poisonbrainbeats.com needs to point to my IP address [IPV4]
DId the same for a Type AAAA DNS record for my.poisonbrainbeats.com that points to my IPV6 address.