fix a bug: smtp.port is ignored when smtp.ssl is true

if the ssl option is turned on, smpt.port shoud be used for sslSmtpPort.

`org.apache.commons.mail.Email` uses `sslSmtpPort` as `MAIL_PORT` if the `sslOnConnect` is true.

```
if (isSSLOnConnect()) {
    properties.setProperty(MAIL_PORT, this.sslSmtpPort);
    ...
}
```

And it's default value is 465

```
protected String sslSmtpPort = "465";
```

So we should call `Email#setSslSmtpPort(String)` to change `MAIL_PORT` when the ssl options is turned on.