core-bundle/src/Resources/contao/library/Contao/Idna.php
public static function encodeEmail($strEmail)
	{
		if ($strEmail == '')
		{
			return '';
		}

		if (strpos($strEmail, '@') === false)
		{
			return $strEmail; // see #6241
		}

		$arrChunks = explode('@', $strEmail);
		$strHost = static::encode(array_pop($arrChunks));

		if ($strHost == '')
		{
			return '';
		}

		return implode('@', $arrChunks) . '@' . $strHost;
	}
public static function encodeEmail($strEmail)
	{
		if ($strEmail == '')
		{
			return '';
		}

		if (strpos($strEmail, '@') === false)
		{
			return $strEmail; // see #6241
		}

		$arrChunks = explode('@', $strEmail);
		$strHost = static::encode(array_pop($arrChunks));

		if ($strHost == '')
		{
			return '';
		}

		return implode('@', $arrChunks) . '@' . $strHost;
	}
Encode the domain in an e-mail address

@param string $strEmail The e-mail address

@return string The encoded e-mail address