[ale] Sendmail Question?

[Gary Maltzen]

At 06:22 PM 7/3/2000 , reji at sbc.edu.ph asked...
>         How does sendmail work? What i mean to say is that how sendmail
>handle the message you want to send including your attached document?

An e-mail message is logically divided in THREE parts

  1) the message envelope
  2) the message header
  3) the message body

When your e-mail program sends a message, it tells sendmail three commands:

  1) who the message is from (MAIL FROM)
  2) who the message is to (RCPT TO)
  3) the message content follows (DATA)

Items 1 and 2 constitute the envelope; the first blank line in the content separates the header from the body. Attachments are just specially encoded body text bracketed by special flag (MIME/UUE) lines.

Sendmail will generally be configured to modify the message header by inserting lines documenting how it received the e-mail for retransmission.

Sendmail will generally examine the headers to avoid e-mail loops by limiting the number of "hops" through which the message passes.

Attachments are generally encoded within the body and are not interpreted by sendmail although sendmail can be configured, for example, to examine the body for suspicious attachment types or names.

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