header  (String)  specifies zero or more header fields, separated by CRLF (i.e. chr(13)+chr(10)) and each conforming to the formatting rules in the appropriate RFC’s (such as RFC 822 and RFC 1521). EMAILX does not check your header items for validity. Note that you may decide to skip this parameter and put all of your header items in the body of the message (see body). Or you can put some here and some in the body parameter (provided you then specify the EMF_HDRCAT flag in opflags.) Here are some sample header lines:

To      : "George Washington" <gw@cherrytree.com>

From    : "Paul Revere" <prevere@patriots.net>

Subject : The Redcoats are Coming

Reply-To: <admin@federalists.org>

cc      : <tj@montebello.net>

Although headers are technically part of the body of the message as far as the SMTP server is concerned, there is a core set of headers that SMTP servers, and especially email readers understand, plus an extended set that most understand, plus a specification for how to define your own headers. See the section on EMAILX Header Specifications for more details.

The Internet email (and most other) standards are documented in a series of "RFC’s" (Request For Comments) which fortunately are very accessible via the Internet; just search for "RFC 822."