Message Collection

Once all recipient names are parsed and verified, the message is collected. The message comes in two parts: a message header and a message body. The header and the body are separated by a blank line.

The header is formatted as a series of lines in this form:

field-name: field-value

For example, a sample header might be:

From: John Smith <Smith@colorado.edu>

field-value can be split across lines by starting the subsequent lines with a space or a tab. Some header fields have special internal meaning and have appropriate special processing. Other headers are simply passed through. Some header fields, like time stamps, may be added automatically.

No formatting requirements are imposed on the message body except that they must be lines of text. sendmail stores the header in memory and stores the body of the message in a temporary file. To simplify the program interface, the message is collected, even if no names are valid. If none of the names are valid, the message is returned to the sender with an error.

With DeskSet(TM) Mail Tool, users can transmit binary data. However, it must be encoded by Mail Tool. The sendmail program does not automatically encode binary data. Refer to the mailtool(1) man page for information about how to encode and decode binary data messages.

The message body is completely uninterpreted and untouched, except that lines beginning with a dot have the dot doubled when transmitted over an SMTP channel. The receiver strips this extra dot.