To send emails programmatically using the Twilio SendGrid API in Java, start by creating a free SendGrid account and obtaining an API key. Store the API key securely, such as by setting it as an environment variable, to avoid exposing sensitive information in your code. Then, add the SendGrid helper library to your project configuration and create a new class with the necessary imports and content for sending an email. Use the API key from an environment variable to authenticate your request and send the email successfully. Once you've sent your first email, explore other features of the Twilio SendGrid API, such as processing incoming mail, adding attachments, and scheduling mail.