Media type / message
message/rfc822
A complete email message with its headers and body, as stored in .eml files and forwarded attachments.
Served inline: Browsers have no renderer for this, so it downloads even without a Content-Disposition header. That makes it the quiet default for anything you do not want opened in place.
Browser behaviour
Downloads
Charset
no charset
Compression
Compress in transit
Send it like this
Content-Type: message/rfc822A binary payload has no character encoding. A charset parameter here is meaningless and occasionally confuses strict parsers.
Handling verdict
Browsers have no renderer for this, so it downloads even without a Content-Disposition header. That makes it the quiet default for anything you do not want opened in place.
A binary payload has no character encoding. A charset parameter here is meaningless and occasionally confuses strict parsers.
The payload is text-like or otherwise repetitive, so gzip or Brotli removes real bytes. Enable it at the server or CDN.
Registered with IANA through a public review process, so the name is stable and every implementation can rely on it meaning the same thing.
Anatomy of the name
RFC 6838Top-level type
message
Message
Subtype
rfc822
Registered in the standards tree.
Structured syntax
none
No suffix, so the payload format is defined entirely by the subtype itself.
Parameters
none
Beyond the charset rule above, this type defines no parameters of its own.
Response headers
Content-Type: message/rfc822
X-Content-Type-Options: nosniff
Content-Disposition: attachment; filename="example.eml"
Vary: Accept-Encodingnosniff stops the browser second-guessing the type you declared, which is what makes the rest of this reliable. Content-Disposition: attachment names the saved file and removes any doubt about rendering.
Server configuration
extension mappingnginx
types {
message/rfc822 eml mime;
}Apache
AddType message/rfc822 .eml .mimeCaddy
@type path *.eml *.mime
header @type Content-Type "message/rfc822"Extensions and other spellings
declaredFile extensions
File signature
No fixed signature — this format has no reliable magic number, so identify it by parsing rather than by the first few bytes.