/** 关闭mail服务器的连接。 */
protected abstract void close() throws MailException;
@Override
public final String toString() {
MapBuilder mb = new MapBuilder().setSortKeys(true).setPrintCount(true);
mb.append("host", getHost());
mb.append("port", getPort());
mb.append("user", getUser());
mb.append("password", getPassword());
mb.append("debug", isDebug());
mb.append("default", isDefault());
mb.append("otherProperties", props);
toString(mb);
return new ToStringBuilder().append(getClass().getSimpleName()).append(mb).toString();
}