Check that your e-mail settings are correct and that your SMTP server is functioning properly. Using QlikView NPrinting Designer, please click File > Options > E-mail settings, check that the settings are correct and send a test message by clicking the Send test E-Mail button. You will be prompted for a To email address. NPrinting then attempts to send a test message and will then display either a success or error message with an error number and description.
Please feel free to contact Support if you are unable to resolve the issue.
NPrinting 17 Designer is only for authoring reports. All settings, such as entering your SMTP server details, are managed in the Server. https://help.qlik.com/en-US/nprinting/17.0/Content/Setup/HowSetUpE-mailNPrinting/Set-up-email.htm
I suggest you use your corporate or ISP's SMTP server for this. Gmail SMTP for example could block applications from sending out e-mails.
HTH - Daniel.