MIME Headers Not Making it Through Gmail API

Question

I\'m trying to automate the creation of drafts via the Gmail API, and I want these drafts to be responses to existing emails. To do this, I believe I need to set the \"threa

Answer 1

Actually, it's a lot simpler than that! If you just supply the correct Subject in the headers, and the correct threadId in the body, Google will calculate all the references for you.

new = MIMEText("This is the placeholder draft message text.")
new["Subject"] = "Example Mail"
new["To"] = "emtholin@gmail.com"
new["From"] = "emtholin@gmail.com"

raw = base64.urlsafe_b64encode(new.as_string())
message = {'message': {'raw': raw, 'threadId': "14ec598be7f25362"}}
draft = service.users().drafts().create(userId="me", body=message).execute()

This results in a draft, ready to be sent in the correct thread:

Then, I send the mail. As you can see, the references are calculated for you:

MIME-Version: 1.0
Received: by 10.28.130.132 with HTTP; Sat, 25 Jul 2015 07:54:12 -0700 (PDT)
In-Reply-To: 
References: 
    
Date: Sat, 25 Jul 2015 16:54:12 +0200
Delivered-To: emtholin@gmail.com
Message-ID: 
Subject: Example Mail
From: Emil Tholin 
To: Emil Tholin 
Content-Type: text/plain; charset=UTF-8

This is the placeholder draft message text.