EmailDLL Online Manual
Purpose: Set the subject line of the message
Handle: The unique ID identifying the email object
Operator: val_SetSubject = 16
Data: text for the subject line
Returns: Success or Error Status
This operator sets the subject line for the email message. While it is a great benefit to the recipient to have a subject header line, this operator is nonetheless optional. You should include a brief summary of the intent or contents of the email on this line. But remember, most email clients display relatively few characters from the subject line in the message list, so shorter is better.
This operator returns an integer indicating whether the operation was performed successfully.