Hello, i am sending an e-mail out of my server via PHP mail function and the mail filtering system used by my server provider (externally, out of my reach) is complaining about sender address being [email protected] Exim fail log: "You do not have sufficient privileges to send mail to this address. Please authenticate and try again." I do not know what is the exact reason that it do not like that sender address. Filtering provider told me the FROM address is the issue. (the hostname.domain.tld is FQDN, has PTR record, fully resolve to IP and vice versa) When i check that e-mail address at http://proxy2.de/email-validation.php it says "The domain hostname.domain.tld has no MX record." But i do not know where i need to create MX record. I already have it on Cloudflare (parent) and also on slave: my server. The domain.tld is hosted on different server than one from which i am sending e-mail, but hostname.domain.tld A record point to right IP (one from which e-mail is sent). level 1 - domain (namesilo) level 2 - cloudflare DNS zone - hostname.domain.tld goes to IP 18.104.22.168 - domain.tld A record goes to 22.214.171.124 - mail.domain.tld is 126.96.36.199 Should i be creating MX at cloudflare, at 188.8.131.52 or at 184.108.40.206 ? e-mail [email protected] is sent from 220.127.116.11 Server is Dovecot 18.104.22.168 mxtoolbox says "Reverse DNS does not match SMTP Banner" as a warning, but i do not know why it should be big problem. Do you have any idea if i can anyhow tweak my DNS configuration so the filtering system managed by my provider is satisfied?