Glossary
What Is RFC 822?
RFC 822 is the internet standard that defined what an email message looks like — published in August 1982 as the "Standard for the Format of ARPA Internet Text Messages." It fixed the shape every email still has today: a block of header fields (Name: value, one per line), a blank line, then the body.
Superseded, but the name stuck
The standard has been revised twice — RFC 2822 (2001), then RFC 5322 (2008), the current "Internet Message Format." But four decades of software were built against "822," so the old name survives: a saved message's MIME type is message/rfc822, and its file extension is .eml. When documentation says "RFC 822 format," read it as "a standard email message."
What RFC 822 covers — and what MIME adds
RFC 822 defined plain-text, ASCII-only messages: From, To, Subject, Date, Message-ID and the rest of the header block, plus a text body. Everything richer — attachments, HTML bodies, non-English characters, inline images — arrived later as MIME (RFCs 2045–2049), which layers structured multi-part content inside an RFC 822 message rather than replacing it. That combination is what mail servers exchange today, and what a .eml file preserves byte for byte.
Why it matters for backups
Because it's the format messages actually travel in, an RFC 822 file is the most faithful copy of an email that can exist — original headers, structure, and attachments, with nothing re-rendered or thrown away. That's why serious archives (InboxBucket included) store the raw RFC 822 message rather than a converted copy. Open one in our EML viewer and you're looking at the message exactly as the receiving server saw it.
FAQ
Is RFC 822 still the current standard?
No — the current Internet Message Format is RFC 5322 (2008), which followed RFC 2822 (2001). The revisions are refinements, not a new format: a valid modern message has the same header/blank-line/body shape RFC 822 defined in 1982, which is why the old name is still used everywhere.
What is message/rfc822?
The MIME content type meaning "a complete email message." You see it when one email is attached inside another — the attached message travels as message/rfc822 — and it's the type of a .eml file.
Is a .eml file the same thing as RFC 822?
Effectively, yes: a .eml file is one message stored in the RFC 822/5322 format, exactly as transmitted — headers, body, and MIME parts intact. That fidelity is what makes .eml the right archival format.
Does RFC 822 support attachments?
Not by itself — 1982 messages were plain ASCII text. Attachments come from MIME, which encodes files as structured parts inside the message body. Every modern email is an RFC 822/5322 envelope with MIME content inside.