wp-includes/PHPMailer/PHPMailer.php:4982Normalize line breaks in a string.
$textstring$breaktypestringoptionalnullstring public static function normalizeBreaks($text, $breaktype = null) { if (null === $breaktype) { $breaktype = static::$LE; } //Normalise to \n $text = str_replace([self::CRLF, "\r"], "\n", $text); //Now convert LE as needed if ("\n" !== $breaktype) { $text = str_replace("\n", $breaktype, $text); } return $text; }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/PHPMailer/PHPMailer.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.