Oder hab ich da was in nem RFC überlesen?
Das steht wohl hier: https://www.rfc-editor.org/rfc/rfc5321.html#section-5.1
ZitatIf an empty list of MXs is returned, the address is treated as if it was associated with an implicit MX RR, with a preference of 0, pointing to that host.
In der älteren Version RFC 2821 stand noch explizit "A RR" drin.
Für Domains ohne MX gibt es daher mittlerweile "Null MX", die in https://www.rfc-editor.org/rfc/rfc7505.txt definiert sind. Das sollte ich mal bei einigen meiner Domains einrichten. Daher danke für die Diskussion hier! ![]()
ZitatInternet mail determines the address of a receiving server through the DNS, first by looking for an MX record and then by looking for an A/AAAA record as a fallback. Unfortunately, this means that the A/AAAA record is taken to be mail server address even when that address does not accept mail. The No Service MX RR, informally called "null MX", formalizes the existing mechanism by which a domain announces that it accepts no mail, without having to provide a mail server; this permits significant operational efficiencies.