RFC 1521:MIME (Multipurpose Internet Mail Extensio...
RFC-Ref

message bod


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... 4. Two additional header fields that can be used to further describe the data in a message body, the Content-ID and Content- Description header fields ...


... header fields optional, and with the specified delimiter not occurring anywhere in the message body, either on a line by itself or as a substring anywhere. Note that the ...
... An access-type of FTP or TFTP indicates that the message body is accessible as a file using the FTP [RFC-959 ...


... header fields optional, and with the specified delimiter not occurring anywhere in the message body, either on a line by itself or as a substring anywhere.> ...



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