datatracker.ietf.org

Minimum required email headers Writing some PHP code and hoping to limit the number of email headers added to my outbound email. [RFC 5322, 3.6](https://datatracker.ietf.org/doc/html/rfc5322#section-3.6) says, "The only required header fields are the origination date field and the originator address field(s). All other header fields are syntactically optional. More information is contained in the table following this definition." That seems incredibly thin and is missing fields such as: "to". [This link](https://wp-mix.com/minimal-optimal-email-headers/) shows the required minimum fields as: * From: * Reply-To: * Content-Type: Does anyone have a definitive list of the minimum accepted email message headers that are accepted by all the main ESPs and won't trigger spam / malware warnings? I'm planning on having DKIM/SPF configured and am planning on stripping internal IPS, sending server type, etc. Thanks.

Minimum required email headers Writing some PHP code and hoping to limit the number of email headers added to my outbound email. [RFC 5322, 3.6](https://datatracker.ietf.org/doc/html/rfc5322#section-3.6) says, "The only required header fields are the origination date field and the originator address field(s). All other header fields are syntactically optional. More information is contained in the table following this definition." That seems incredibly thin and is missing fields such as: "to". [This link](https://wp-mix.com/minimal-optimal-email-headers/) shows the required minimum fields as: * From: * Reply-To: * Content-Type: Does anyone have a definitive list of the minimum accepted email message headers that are accepted by all the main ESPs and won't trigger spam / malware warnings? I'm planning on having DKIM/SPF configured and am planning on stripping internal IPS, sending server type, etc. Thanks.