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RFC Compliant Emails


In the world of computer communications, a Request for Comments (RFC) is a publication published by the Internet Engineering Task Force (IETF) describing methods and behaviours applicable to computing, networking, and the internet as a whole.

Many anti-spam and email services have been programmed or can be configured to reject messages that do not comply to the standard for internal email. For example, if an attachment does not follow the exact structure for a particular file type.

An email is broken down into many parts such as the SMTP headers, message senders, message recipients, message content, and attachments are all checked for correct formatting and RFC compliance. A typical example of an RFC compliance check would be to validate if the sender domain contains no more than one dot in a row such as; mail from: external-domain..com, if the sender domain contains more than one as the case here, this would fail an RFC compliance check.

You can read the full RFC 821 document for RFC compliant email requirements.

Further Reading

Wikipedia's guide to RFC