MailKit: How to reply to Gmail conversation

Question

I am using MailKit to reply to an email received from a Gmail account. I set the value of the In-Reply-To and References header as described in the MailKit documentation:

if (!string.IsNullOrEmpty(replyMessage.MessageId)) {
    message.InReplyTo = replyMessage.MessageId;
        foreach (var id in replyMessage.References) {
            message.References.Add(id);
        }
    message.References.Add(replyMessage.MessageId);
}

Given this, I expect the reply mail to show up in Gmail as a reply to the original message. However, this does not happen. The mail is shown like any other random new mail. Am I missing something?

Answer 1

You also need to set to message.Subject to “Re: “ + replyMessage.Subject