D. J. Bernstein
Internet mail

Internet mail infrastructure


Responsibilities and envelopes
Moving a message closer to a remote recipient
MXPS: the Mail Exchanger Protocol Switch

CNAME records in mail
IP addresses in mail

These pages explain the Internet mail infrastructure. There are separate pages describing the Simple Mail Transfer Protocol, which is used to transfer mail between Internet hosts.

Programs that read mail divide each message into a header and a body. There are separate pages describing the header format.

Usually the body of a message is human-readable text. However, users often ``attach'' files in other formats. For example, uuencode is a simple method of safely encoding any binary file as lines of text inside a message. The most popular structure for attachments is MIME, which includes a file-format naming scheme. MIME is not discussed here.

Once a message is delivered to a user's mailbox on a central server, the user can log in to the server and retrieve the message. The most popular protocol dedicated to this task is POP. Another protocol, offering many more mailbox-processing features, is IMAP. POP and IMAP are not discussed here.