Sorry I got to this late.
I can confirm setting both the MessageID in the “In-Reply-To” or “References” field (as an array or csv) will work.
Some email providers like Gmail prefers “In-Reply-To”, while others use the “References” field, so it is wise to just fill in both fields in case the recipient doesn’t use Gmail.
Here is my current setup:
You can also use the Gmail “Make an API Call” module to create a draft.
For more information and other related questions (like original copy and signatures), see
- Method: users.drafts.create | Gmail | Google for Developers
- email - How to open a draft created with Gmail API in browser? - Stack Overflow
- node.js - How to create draft in gmail api - Stack Overflow
- python - How to create a draft message in existing thread with gmail API - Stack Overflow
- While trying to create draft replies to threads using Gmail API, Original email content is not appended in the draft message - Stack Overflow
- php - Sending email with signature using Gmail API - Stack Overflow
- How to include the users Gmail signature when using GmailApp.sendEmail from Google Sheet - Stack Overflow
- How to quote original message in reply using Gmail API in apps script? - Stack Overflow
- python - Sending reply to existing message using gmail api does not show conversation trail in the gmail inbox - Stack Overflow
Hope this helps! Let me know if there are any further questions or issues.
Did you know, this forum has a Hire a Pro category, where you can post your request for off-site specialised help on other platforms (video call/screenshare/private messaging/etc.)? This may help you get your issue resolved faster especially if it is urgent. It is important to post your request in the Hire a Pro category, as forum members are not allowed to advertise their services (even offer FREE assistance to help) in other categories like here. Once you have posted in the Hire a Pro category, that will allow other members like me to provide booking links to our calendars for a free consultation and video assistance (including screenshare)!
— @samliew
P.S.: Investing some effort into the Make Academy will save you lots of time and frustration using Make.