The message header pwcHeaders usually contains information, such as the name and address of the sender and receiver of the message. It consists of one or more entries, each of which contains two fields: Name and Value. Both fields are Unicode strings that can be read with MailGetField and modified with MailSetField. Entries a message header might contain are described in the following table.
| Name Field | Value Field |
|---|---|
| To | john@street.com |
| From | frank@hill.com |
| cc | bob@river.com |
| Subject | The way it was, is and will be |
When creating a message header string, you should terminate the Name and Value strings with a NULL character. For the last Value field, you must terminate it with two NULL characters to indicate the end of the header.
For the most part, the strings assigned to the Name fields have no special meaning to the system, unless the string is "Type." In this case, the system checks the corresponding value field to see if it matches the name of a dynamic-link library (DLL) registered with the system. The body of the message is passed to the DLL for processing.