Which libraries are commonly used in PHP for secure email transport?

PHPMailer and SendGrid are indeed commonly used libraries for secure email transport in PHP. PHPMailer is a widely used library that simplifies the process of sending emails via PHP, ensuring secure SMTP connections with support for features such as HTML messages, file attachments, and more. It is known for its ease of use and flexibility, making it a popular choice among PHP developers.

SendGrid, on the other hand, is a cloud-based service that provides an API for sending emails securely. It is often utilized in conjunction with PHP libraries like PHPMailer to handle email delivery efficiently, ensuring proper authentication and delivering high-volume emails securely.

The combination of these two provides a robust solution for sending secure emails, with PHPMailer's capability to interface with SMTP servers and SendGrid's infrastructure for effective email routing and management. This makes the first choice particularly suitable for developers looking for reliable and secure email transport options.