Via API: Create & Send an Estimate

Hi,

I've got an already created contact, which has an email address associated with it. If I use the web interface, I am able to create an estimate and send it through seamlessly.

However, when I create the estimate, I am able to create it fine, using these options:

{ customer_id: '[blanked]',
organization_id: '[blanked]',
estimate_number: '25 by Jacob Zuma',
template_id: '[blanked]',
date: '2016-02-13',
expiry_date: undefined,
exchange_rate: 1,
discount: 0,
is_discount_before_tax: true,
discount_type: 'item_level',
is_inclusive_tax: 'false',
custom_body: '',
custom_subject: '',
salesperson_name: '',
custom_fields:
[ { index: 1, value: 'param' },
{ index: 2, value: undefined },
{ index: 3, value: '60' },
{ index: 4, value: '50 weeks' } ],
line_items:
[ { rate: '100',
unit: '',
item_order: 0,
quantity: '',
discount: 0,
description: 'Something funny yeah' } ],
notes: undefined,
terms: undefined,
shipping_charge: 0,
adjustment: 0,
adjustment_description: '' }

I then post to /estimates, and I've also tried supplying send=true. This seems to work fine. However, unlike normal estimates, when I edit it via the web interface, this box is not ticked: