The idea is:
Add the headers “In-Reply-To” and “References” to Send Email (SMTP) node, to allow sending emails as replais to recieved emails.
My use case:
I want to reply an incoming email from n8n itself with an automated message. Now I just add "Re: " at the beggining of the subject, and mdoern email clients like Gmail treat this as a reply. But it is not the best way to do it, as it is very superficial. A better way to do it is to add the email ID (which is delivered to me on the Recieve email via IMAP node) at the “In-Reply-Tio” and “References” headers on SMTP, but this is not possible on the SMTP node on n8n.