I am trying to have forward appear in the same thread when sending message with gmail API (which gmail/inbox is doing perfectly fine from the UI).
This is working fine when I reply (I am adding the threadId, the 'Re: ' and using the RFC 2822 convention (with 'In_Reply_To' and 'References' headers)) but when I try to forward a message from a thread (the only difference with previously is that I put 'Fwd: ' instead of 'Re: ' in front of the subject) it will appear outside of the thread on the gmail UI.
What am I doing wrong? How does google keep forwarded message in the same thread? (I am working with the Python API if this is of any help)
Thanks a lot,