Microsoft Graph: How to send emails in the same thread, without needing a client's reply first

Question

Is there a way to send an email via Microsoft Graph with references or in-reply-to headers applied?

I've looked at

• Cannot pass "In-Reply-To" parameter to Microsoft Graph sendMail
• https://github.com/microsoftgraph/microsoft-graph-docs/issues/6256
• How do I add In-Reply-To and References to 'Send mail'?

All of these seem to address when replying to a client's response. E.g.) User sends an email to client >> Client sends a reply back >> User sends a reply.

I need a way to thread the emails even if I send them 2 emails back to back. E.g.) User sends an email to client >> User sends a follow up email to client.

Microsoft Graph API's reply endpoints seems to overwrite any toRecipient you pass through, and automatically will send the email to the Sender of the previous email:

Reply to the sender of a message using either JSON or MIME format.

• https://learn.microsoft.com/en-us/graph/api/message-reply?view=graph-rest-1.0&tabs=http

So if I were to...

From: me@hotmail.com

To: client@gmail.com

1. Send the initial email via /me/messages/{id}/send
2. Then immediately send a follow up email via /me/messages/{id}/reply,

It just sends up sending the reply to myself, me@hotmail.com; since Microsoft Graph specifically states that it replies to the sender. In this instance, I'm just replying to my own message.

Answer 1

The Send message endpoint sends an existing draft message.

The draft message today can be a new message draft, reply draft, reply-all draft, or a forward draft. Refer documentation here.

Being said that, consider filing user voice for your specific ask so it could be considered for future implementations.