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Multiple From: fields are allowed by https://tools.ietf.org/html/rfc5322#section-3.6.2 https://tools.ietf.org/html/rfc5322#section-3.6.2 as long as a Sender: is

• KasparEtter 5y ago
  Just to be precise: It's a single From field with several addresses, not multiple From fields (see https://tools.ietf.org/html/rfc5322#page-21 https://tools.ietf.org/html/rfc5322#page-21). RFC 6854 updated the From field to allow an empty group construct (see https://explained-from-first-principles.com/email/#no-reply https://explained-from-first-principles.com/email/#no-reply) but mainly for other reasons (see https://explained-from-first-principles.com/email/#email-address-internationalization https://explained-from-first-principles.com/email/#email-add...). DMARC authentication either rejects multiple addresses in the From field or authenticates them all and applies the most strict policy (see https://explained-from-first-principles.com/email/#domain-based-message-authentication-reporting-and-conformance https://explained-from-first-principles.com/email/#domain-ba...).