Email sending failed: Could not load or process image

<m:attachment fileName="Diagram.xls">
            <e:workbook >
                <e:worksheet >
                    <e:image startRow="1" startColumn="1"
                             URI="#{backBean.imageURI}"/>
                </e:worksheet>
           </e:workbook>
</m:attachment>

public String imageURI() {
       
        // create dataSet
        DefaultCategoryDataset dataset = new DefaultCategoryDataset();
        ...
        // create chart
        JFreeChart chart = ChartFactory.createLineChart(
                "Calls/Staff", // chart title
                "Date", // domain axis label
                "Count", // range axis label
                dataset, // data
                PlotOrientation.VERTICAL, // orientation
                true, // include legend
                true, // tooltips?
                false // URLs?
                );
                
        // save the chart into the image
        String fileUri = null;
        try{
            File file = File.createTempFile("report","jpg");
            ChartUtilities.saveChartAsJPEG(file, chart, 1000, 400);
            fileUri = file.toURI().toString();            
        }catch(IOException e){            
            e.printStackTrace();
        }
        return fileUri;
    }

 // удаляем временные файлы после отправки мейла
        try {            
            File file;           
                file = new File(new URI(fileURI));
                file.delete();            
        } catch (Exception e) {
        }

File.createTempFile("chart","jpg"); 

new File(System.getProperty("java.io.tmpdir")+"chart.jpg");