How to send a reference header in a transmission request in Sparkpost

I use Sparkpost to send emails and a number of my users use gmail to read them. Gmail has a feature to group emails in a conversation when they have the same subject, similar dates and senders.

I want to send several emails to a single user but I do not want gmail to group them. For example, if I send an email with a pin code, I do not want gmail to group it with previous emails with the same subject.

In gmail documentation it says you can avoid this grouping changing the sender or the subject.

But it says you can also send a different reference header, which seems cleaner.

In Sparkpost, in the transmission API, you can send an Object containing "headers other than Subject, From, To, and Reply-To".

I assume that you can send something like this:

content: {
  headers: {
    references: "12345678901234567890"
  from: {
    name: "John Doe",
    email: ""
  subject: "this is my subject",
  html: "<h1>Welcome</h1>"

Has anyone tried it. Is this correct?