Question: Can we override the "X-Mailer" header value and replace it with something else using RemoveHeaderField and AddHeaderField? Not that we don’t want to promote Chilkat, but we want to also promote our app. Would this also apply to the "Message-ID"?
Answer: Yes, you can use AddHeaderField/RemoveHeaderField for X-Mailer and Message-ID. The email object also has a Mailer property which is the same as getting/setting the X-Mailer header field. The Message-ID can be set, but if you do so, you should disable the mailman.AutoGenMessageId property to prevent the mailman from generating a unique message-id with each email sent. Some SMTP servers will discard "duplicates" if the same message-id is used more than once. Many applications tend to use the same instance of an email object to send the same email to more than one recipient. Chilkat will automatically generate a new/unique message ID during the message sending process to prevent duplicates. If you turn off AutoGenMessageId, you have complete control over the Message-ID header field.