I am using the Gmail API to draft email replies.

The email response should contain the thread history which can be displayed by clicking a small button ‘Show trimmed content’.
I have set all the correct IDs: thread id, In-Reply-To, References etc however it sometimes doesn’t work and just renders the text as normal text without the hidden content. I don’t understand why sometimes it renders and sometimes doesn’t.

I’m just doing a regular text response currently, not using html.
To do this I am appending > to the beginning of each line.

Like I said, sometimes this works and others does not.

Is it based on whats in the content?

Please advise!