SSL error when using phpMailer with smtp

I get the following error message when I'm trying to use phpMailer with Zoho mail:

2016-09-04 09:31:19 Connection: opening to ssl://smtp.zoho.com:587, timeout=300, options=array ( ) 2016-09-04 09:31:20 Connection: Failed to connect to server. Error number 2. "Error notice: stream_socket_client() [ function.stream-socket-client]: SSL operation failed with code 1. OpenSSL Error messages: error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol 2016-09-04 09:31:20 Connection: Failed to connect to server. Error number 2. "Error notice: stream_socket_client() [ function.stream-socket-client]: Failed to enable crypto 2016-09-04 09:31:20 Connection: Failed to connect to server. Error number 2. "Error notice: stream_socket_client() [ function.stream-socket-client]: unable to connect to ssl://smtp.zoho.com:587 (Unknown error) 2016-09-04 09:31:20 SMTP ERROR: Failed to connect to server: (0) 2016-09-04 09:31:20 SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

$mail = new PHPMailer();

$body = '---Test---';

$mail->SMTPDebug = 3;

$mail->IsSMTP();

$mail->SMTPAuth = true;

$mail->Host = "smtp.zoho.com";

$mail->Port = 587;

$mail->Username = 'example@zoho.com';

$mail->Password = 'password';

$mail->SMTPSecure = 'ssl';

$mail->SetFrom('example@zoho.com', 'Web Page');

$mail->Subject = "Hello";

$mail->AltBody = '---Test---';

$mail->MsgHTML($body);

$mail->AddAddress('email');

$mail->Send();

Any ideas what's wrong?