How to Send HTML Emails in PHP using SMTP or email API

PHP can send HTML email through its native mail() function, PHPMailer, SymfonyMailer, or the Mailtrap PHP Client, with PHPMailer and SymfonyMailer generally recommended because they support authenticated SMTP, TLS/SSL, attachments, embedded images, multiple recipients, and external providers. The built-in mail() function can send basic HTML messages when appropriate MIME and content-type headers are set, but it relies on the local server, has weaker deliverability and security characteristics, and makes attachments, CID images, bulk delivery, and third-party SMTP connections difficult. Images sent through mail() may be externally hosted or base64-encoded, though base64 increases message size and may be blocked by clients. PHPMailer provides SMTP configuration, HTML and plain-text alternative bodies, CID-based images, attachments, recipient loops, and error reporting, while SymfonyMailer offers comparable capabilities along with configurable transports, Twig templates, CSS inlining, and several attachment and embedding methods. Mailtrap’s SDK supports API-based sending, templates with Handlebars variables, custom headers, categories, recipient fields, embedded images, and secure API-key management through environment variables. The material also outlines using PHP and PHPMailer for HTML emails submitted from contact forms, emphasizing input validation, sanitization, CAPTCHA verification, and exception handling.

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