Re: Pre-RFC discussion about adding a DNS function for Null MX handling

On Wed, 13 May 2026 01:47:23 +0000, Samuel Fontebasso wrote: > Proposed behavior: > - false when there are no MX records; > - false when all MX records are Null MX records; > - true when at least one MX record has an exchange target other than ".". > > This would not validate email deliverability or perform SMTP-level checks. > It would only provide a DNS-level distinction between "has an MX record" > and "has a non-null MX record”. I’d say this isn’t that useful because the absence of an MX record does not mean that a domain cannot receive email. While the RFC7505 “null MX” approach is not handled explicitly in PHP functions, the fallback of using the A record as an MX still applies, as per https://datatracker.ietf.org/doc/html/rfc974 and https://www.rfc-editor.org/rfc/rfc5321#section-5.1 So of those three proposed behaviours, only one is actually useful. Marcus