Version 2.3.9 * 7506: resolves issues when UTF-8 values are used in Mail headers, particularly addresses. * 7507: ensures that array values can be used with cookies. * 7514: ensures that multipart MIME messages can be added to Zend\Mail\Message instances in such a way that they do not conflict with ZF2015-04.

Version 2.3.8 * ZF2015-04: Zend\Mail and Zend\Http were both susceptible to CRLF Injection Attack vectors (for HTTP, this is often referred to as HTTP Response Splitting). Both components were updated to perform header value validations to ensure no values contain characters not detailed in their corresponding specifications, and will raise exceptions on detection. Each also provides new facilities for both validating and filtering header values prior to injecting them into header classes. If you use either Zend\Mail or Zend\Http (which includes users of Zend\Mvc), we recommend upgrading immediately.