Seldaek/monolog · error · InvalidArgumentException

The encoding can not contain newline characters to prevent e

Error message

The encoding can not contain newline characters to prevent email header injection

What it means

Error "The encoding can not contain newline characters to prevent email header injection" thrown in Seldaek/monolog.

Source

Thrown at src/Monolog/Handler/NativeMailerHandler.php:166

     */
    public function setContentType(string $contentType): self
    {
        if (strpos($contentType, "\n") !== false || strpos($contentType, "\r") !== false) {
            throw new \InvalidArgumentException('The content type can not contain newline characters to prevent email header injection');
        }

        $this->contentType = $contentType;

        return $this;
    }

    /**
     * @return $this
     */
    public function setEncoding(string $encoding): self
    {
        if (strpos($encoding, "\n") !== false || strpos($encoding, "\r") !== false) {
            throw new \InvalidArgumentException('The encoding can not contain newline characters to prevent email header injection');
        }

        $this->encoding = $encoding;

        return $this;
    }


    protected function mail(string $to, string $subject, string $content, string $headers, string $parameters): void
    {
        mail($to, $subject, $content, $headers, $parameters);
    }
}

View on GitHub (pinned to 57eb102834)

When it happens

Trigger: Thrown at src/Monolog/Handler/NativeMailerHandler.php:166 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Seldaek/monolog@57eb102834 (2026-08-17). Data as JSON: /api/errors/f3e1319d22b2ceba. Report an issue: GitHub.