Office.context.mailbox.item.internetHeaders.setAsync fails on Classic UI when replying/forwarding .eml file

[AtharvaDevSeclore]

Office.context.mailbox.item.internetHeaders.setAsync fails on Classic UI when replying/forwarding .eml file

Your Environment

• Platform: Mac
• Host: Outlook 16.91

Expected behavior

Office.context.mailbox.item.internetHeaders.setAsync should be successful

Steps to reproduce

1. compose a mail
2. click on file -> save as and save the mail on the device as savedMail.eml
3. open the folder containing savedMail.eml
4. ctrl+click on savedMail.eml and open in outlook
5. reply/forward mail
6. open inspect element window
7. try to set internet headers

Office.context.mailbox.item.internetHeaders.setAsync(
  { "preferred-fruit": "orange", "preferred-vegetable": "broccoli", "best-vegetable": "spinach" },
  function (asyncResult) {
    if (asyncResult.status === Office.AsyncResultStatus.Succeeded) {
      console.log("Successfully set headers");
    } else {
      console.log("Error setting headers: " + JSON.stringify(asyncResult.error));
    }
  }

Current behavior

Office.context.mailbox.item.internetHeaders.setAsync fails on classic UI with error code 5001

Provide additional details

I observed this issue only in classic UI. modern UI is working as expected

[mobisw-msft]

Hey @AtharvaDevSeclore ,

We are investigating this issue and will get back to you shortly.