code to get all followers' emails
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followers = self.env['mail.followers'].search([('res_model', '=', 'sale.order'), ('res_id', '=', sale_order_id)])
emails = [follower.partner_id.email for follower in followers]
Add these emails to the Cc field
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email_values = {
'subject': 'Sales Order Notification',
'email_to': main_recipient_email,
'email_cc': ','.join(emails),
# other email parameters
}
mail = self.env['mail.mail'].create(email_values)
mail.send()