// PUT admin/posts/5b7ada404f87d200b5b1f9c8/?newsletter=weekly-newsletter&email_segment=status%3Afree
{
    "posts": [
        {
            "updated_at": "2022-06-05T20:52:37.000Z",
            "status": "published"
        }
    ]
}

{
    "posts": [
        {
            "id": "5ddc9141c35e7700383b2937",
            ...
            "email": {
                "id": "628f3b462de0a130909d4a6a",
                "uuid": "955305de-d89e-4468-927f-2d2b8fec88e5",
                "status": "failed",
                "recipient_filter": "all",
                "error": "Email service is currently unavailable - please try again",
                "error_data": "[{...}]",
                "email_count": 2,
                "delivered_count": 0,
                "opened_count": 0,
                "failed_count": 0,
                "subject": "Welcome",
                "from": "\"Weekly newsletter\"<noreply@example.com>",
                "reply_to": "noreply@example.com",
                "html": "...",
                "plaintext": "...",
                "track_opens": true,
                "submitted_at": "2022-05-26T08:33:10.000Z",
                "created_at": "2022-06-26T08:33:10.000Z",
                "updated_at": "2022-06-26T08:33:16.000Z"
            },
            ...
        }
    ]
}
To send a post by email, the newsletter query parameter must be passed when publishing or scheduling the post, containing the newsletter’s slug. Optionally, a filter can be provided to send the email to a subset of members subscribed to the newsletter by passing the email_segment query parameter containing a valid NQL filter for members. Commonly used values are status:free (all free members), status:-free (all paid members) and all. If email_segment is not specified, the default is all (no additional filtering applied). Posts are sent by email if and only if an active newsletter is provided. 
// PUT admin/posts/5b7ada404f87d200b5b1f9c8/?newsletter=weekly-newsletter&email_segment=status%3Afree
{
    "posts": [
        {
            "updated_at": "2022-06-05T20:52:37.000Z",
            "status": "published"
        }
    ]
}
When a post has been sent by email, the post object will contain the related newsletter and email objects. If the related email object has a status of failed, sending can be retried by reverting the post’s status to draft and then republishing the post. 
{
    "posts": [
        {
            "id": "5ddc9141c35e7700383b2937",
            ...
            "email": {
                "id": "628f3b462de0a130909d4a6a",
                "uuid": "955305de-d89e-4468-927f-2d2b8fec88e5",
                "status": "failed",
                "recipient_filter": "all",
                "error": "Email service is currently unavailable - please try again",
                "error_data": "[{...}]",
                "email_count": 2,
                "delivered_count": 0,
                "opened_count": 0,
                "failed_count": 0,
                "subject": "Welcome",
                "from": "\"Weekly newsletter\"<noreply@example.com>",
                "reply_to": "noreply@example.com",
                "html": "...",
                "plaintext": "...",
                "track_opens": true,
                "submitted_at": "2022-05-26T08:33:10.000Z",
                "created_at": "2022-06-26T08:33:10.000Z",
                "updated_at": "2022-06-26T08:33:16.000Z"
            },
            ...
        }
    ]
}