MailItem Message ID Changes After Sending — Causes ‘Item Not Found’ on Lookup

Describe the bug

We are using Microsoft Graph to create and send emails in the following way:

1. Create a draft message
   var draftMessage = await graphClient.Users[userEmail].Messages.PostAsync(message);
2. Send the draft message
   await graphClient.Users[userEmail].Messages[draftMessage.Id].Send.PostAsync();
3. Get the sent message using its internetMessageId
   After sending, we try to retrieve the sent message by filtering with its internetMessageId:

var filter = $"internetMessageId eq '{draftMessage.InternetMessageId}'";

var messageCollectionResponse = await graphClient.Users[userEmail].Messages.GetAsync(
    requestConfiguration => requestConfiguration.QueryParameters.Filter = filter
);

The issue is
When we create the draft, we receive an initial message.Id.

After sending the message, we can look it up successfully using the internetMessageId.
However, after some time, the original messageId becomes invalid — it changes in the mailbox, and trying to retrieve the message by the old ID results in an ErrorItemNotFound error.

Expected behavior

The messageId returned when creating or sending the message should remain consistent and valid

How to reproduce

.

SDK Version

5.16.0

Latest version known to work for scenario above?

No response

Known Workarounds

No response

Debug output

</details>


### Configuration

_No response_

### Other information

_No response_

Start with the create-draft, send, and internetMessageId lookup calls shown in the issue, then reproduce the delayed lookup failure against Microsoft Graph. Compare the returned message IDs before and after sending and determine whether the behavior is in the SDK or the service; done means documenting the cause and an actionable resolution or workaround.