X-Reply-To header not changing Reply-To in Microsoft Graph API

Question

Here is what I'm doing in my API call:

Creating a Message object

Setting the X-Reply-To header to my custom email:

**message.Headers.Add("X-Reply-To", "custom@email.com");**

Sending the email via the Graph API

When looking at the full headers of the sent message, I can see the X-Reply-To field populated correctly. But the Reply-To remains unchanged.

I expected that setting X-Reply-To would override or change the Reply-To field as well, but that doesn't seem to be the case.

Is there something else I need to do to get X-Reply-To to actually modify Reply-To when sending through the Graph API? Or is this not possible and I have to find another approach?

Any help or insights appreciated! I'm using Microsoft 365 with the latest Graph API.

Answer 1

The replyTo property is strongly typed in the Graph so you just need to use that property in you request eg

{
    "message": {
        "subject": "Meet for lunch?",
        "body": {
            "contentType": "Text",
            "content": "The new cafeteria is open."
        },
        "toRecipients": [
            {
                "emailAddress": {
                    "address": "target@domain.com"
                }
            }
        ],
        "replyTo": [
            {
                "emailAddress": {
                    "address": "replyto@domain.com"
                }
            }
        ]
    }
}

Answer 2

The ReplyTo does get added to the email by adding "x-Reply-To"through Microsoft Graph API.

@DJ-MoMo That is incorrect. That header is sent by MS Graph, but it is not set by you as a header. As of July 8, 2024, only custom headers are supported.

replyTo is sent in the payload since, just like "body", "subject", and "toRecipients", it is a property of the message resource.

If the address is not changed after being sent correctly, it's either an MS Graph error or an Entra authorization issue.