Roundcube and SMTP Error (-1) : Connection to server failed

In case you are having problems to configure Roundcube to send mail, please note the following:

If you are connecting on port 587 you should probably use tls:// instead of ssl:// because (by default) STARTTLS is used on port 587. In case you are using port 465 you should use the ssl:// prefix, because this is the default port for SSL.