Incorrect Conversation ID Returned by Microsoft Graph API for Unrelated Emails

Question

Dear Microsoft Support Team,

We are encountering an issue with the Microsoft Graph API where the GET https://graph.microsoft.com/v1.0/me/messages/{message-id} response appears to be returning an incorrect conversationId.

We have identified two separate emails that do not belong to the same email thread or conversation. However, the API response for both emails contains the same conversationId, even though they are clearly unrelated.

This behavior is causing issues in our application, as we rely on the conversationId to correctly identify and group emails belonging to the same conversation.

For your reference, we have attached the complete Microsoft Graph API responses for both emails.

Could you please help us understand:

Why two unrelated emails are returning the same conversationId?

Under what scenarios can this behavior occur?

Is this expected behavior, or could it indicate an issue with the API or mailbox data?

Are there any additional properties that you recommend using to accurately determine whether two emails belong to the same conversation?

We would appreciate your assistance in understanding the root cause of this behavior.

Please let us know if you require any additional information, such as the mailbox type, tenant details, request IDs, or any other diagnostic information.

Thank you for your support.

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Answer 1

Dear @Swapnil Jagtap,

Based on the information shared, the only common property between the two messages is conversationId. However, a matching conversationId alone is not sufficient to conclude that two messages belong to the same logical email thread. Exchange generates this value using internal conversation-grouping logic, and Microsoft does not recommend relying on it as the sole indicator of message relationships.

I also found similar discussions from other Microsoft Graph users reporting unexpected conversation-threading behavior involving conversationId. At this time, I was unable to find Microsoft documentation that explicitly describes all scenarios where unrelated messages may receive the same conversationId.

• Conversation id changes after editing subject?
• Sometimes the Conversation ID changes when a user replies to an email

From my perspective view, it is recommended to review additional message properties when determining whether two emails belong to the same conversation, including:

• internetMessageId
• In-Reply-To
• References
• ConversationIndex

These properties typically provide more reliable threading information than conversationId alone and can help validate whether a relationship exists between the messages.

Based on the information currently available, I would not recommend treating the two messages as related solely because they share the same conversationId. If the properties listed above do not indicate a relationship, it may be appropriate to treat them as separate conversations from an application-design perspective.

As a next step, I recommend reviewing the properties above within your environment to determine whether they establish a direct threading relationship between the two messages.

Thank you very much for your valuable time and your cooperation.