wp_mail() is a wrapper for PHPMailer which is a wrapper for PHP’s mail().
bool wp_mail(
string $to,
string $subject,
string $message,
[string|array $headers = ''
[, string|array $attachments = array() ]
]
)
A header must follow the form Name:Content, eg.: Bcc:hello@example.com. Multiple headers might be separated by \n or passed as an array.
An attachment is a path in the local file system. See PHPMailer::AddAttachment() for details.
In contrast to the raw mail() function, the WordPress wrapper is a pluggable function: it can be replaced by plugins. This is useful in when the installation needs specific smtp configuration. But this means also wp_mail() is not available before plugins_loaded has been called.
PHPMailer is a class delivered by WordPress but developed outside. It handles many edge cases.
Always use wp_mail(), never mail().
