The latest version has been tested with 1.3 without issues. It also supports the new user state in 1.3 (bounced email). Did you encounter any error or else?
Email to twiqolia@hotmail.com failed: Unable to Connect to ssl://mandrillapp.com:443. Error #0: php_network_getaddresses: getaddrinfo failed: Temporary
Zend_Http_Client_Adapter_Exception: Email to twiqolia@hotmail.com failed: Unable to Connect to ssl://mandrillapp.com:443. Error #0: php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution - library/Zend/Http/Client/Adapter/Socket.php:235
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Unable to Connect to ssl://mandrillapp.com:443. Error #0: php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution
Zend_Http_Client_Adapter_Exception: Unable to Connect to ssl://mandrillapp.com:443. Error #0: php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution -library/Zend/Http/Client/Adapter/Socket.php:235
I m getting too many errors like these and, errors was started when upgraded to 1.3.