Twilio SendGrid has achieved a significant improvement in its inbox protection rate, reaching 99.99% in Q2 2019 and further increasing it to four nines of protection for the world's email ecosystem. This improvement is attributed to the development of a machine learning model called Phisherman, which identifies phishing emails in-flight and prevents them from being sent. The model is trained using a vast knowledge base of abusive email content and utilizes TensorFlow neural networks to determine the probability that any given piece of email is phish. With this advancement, Twilio SendGrid aims to prevent phishing attacks on businesses' top management echelons and protect users from devastating effects of such attacks.