Outlook addin with office.js giving Host error with code 5000 for item.sendAsync()

Question

I'm trying to send an email using the Outlook's office.js API's item.sendAsync() method which triggers on custom send button added on taskpane from a task pane add-in. However, I'm getting a Host Error with the following response:

{
  "code": 5000,
  "message": "The operation is not supported.",
  "name": "Host Error"
}

Here is the code snippet I am using

item.sendAsync((result) => {
    if (result.status === Office.AsyncResultStatus.Succeeded) {
        document.getElementById('review-message').innerHTML = 
            '<p class="ms-font-xs" style="color: green;">✅ Email sent successfully via sendAsync!</p>';
        
        // Close task pane after short delay
        setTimeout(() => {
            if (window.close) {
                window.close();
            }
        }, 2000);
    } else {
        console.error('sendAsync failed:', result.error);
        const error = result.error;
    }
});

I am using it on Outlook for Mac (version 16.102) Also I have added below permission in mainfest.xml

  <Permissions>ReadWriteMailbox</Permissions>

I want to acheive below functionality in my addIn

Display email data on taskpane also having custom send button
send from custom send button available in taskpane (so above code snippet is triggered on button click)

sendAsync() probably causing this error because you are triggering this function on a button in UI, while sendAsync() method only works in compose mode and can only be triggered UI-less command function (from the ribbon) although it cannot be called from the UI. — Faizan Ahmad
– Faizan Ahmad, Commented Sep 23 at 8:54

Sean Laberee - Microsoft · Accepted Answer · 2025-09-19 20:42:54Z

0

The api you are trying to use is in Mailbox 1.15 Requirement Set (https://learn.microsoft.com/en-us/javascript/api/outlook/office.appointmentcompose?view=outlook-js-preview#outlook-office-appointmentcompose-sendasync-member(1)) which isn't yet fully implemented on Outlook for Mac which is likely the cause here.

answered Sep 19 at 20:42

Sean Laberee - Microsoft

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1 Comment

sudhanshud Sep 22 at 10:46

is there any option similar functionality ( to send on click of send button from taskpane) can be acheived in outlook for mac ( for Mailbox 1.14 or below) ?

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