#include <QDesktopServices>

void MyClass::slotSendFileViaEmail(const int itemId)
{
    const QString fileName = getFileFromItemId(itemId);
    
    // Logic in program checks existence of file somewhere else
    // and this slot should be called only in case it exists.
    Q_ASSERT(QFileInfo(fileName).exists());
    
    // Version 1
    QDesktopServices::openUrl(QUrl("mailto:?subject=File from our app.&attach=" + fileName));
    
    // Version 2
    QDesktopServices::openUrl(QUrl("mailto:?subject=File from our app.&attachment=" + fileName));
}

#include <QMessage>
#include <QMessageService>
#include <QFileInfo>

QTM_USE_NAMESPACE;

void MyClass::slotSendFileViaEmail(const int itemId)
{
    const QString fileName = getFileFromItemId(itemId);
    
    // Logic in program checks existence of file somewhere else
    // and this slot should be called only in case it exists.
    Q_ASSERT(QFileInfo(fileName).exists());
    
    QStringList attachment;
    attachment.append(fileName);
    
    QMessage msg;
    msg.setType(QMessage::Email);
    msg.setSubject("File from our app.");
    msg.setBody("File from our app is included in attachement.");
    msg.appendAttachments(attachment);
    
    QMessageService msgService;
    // User will fill reciver email, can write additional info,
    // etc. and finally send.
    bool success = msgService.compose(msg);
    
    if(!success) {
        // Send info for example via QMessageBox
    }
}