EMailSender-master Library problem to manage email variable

First of all, thank you so much for creating such a great library. My problem is: The code works perfectly. EMailSender::Response resp = emailSend.send("xxxxx@gmail.com", message); However; When I use it like this, it gives me an error. myemail="xxxxx@gmail.com" EMailSender::Response resp = emailSend.send(myemail, message); no matching function for call to 'EMailSender::send(String*, EMailSender::EMailMessage&)' Couldn't figure out the problem. Can you please point to me to the right direction? Thanks.