If you use SqlBak to send backups to FTP Server, you can face a problem when though the connection seems to work, the file transfer doesn’t. In this way, you may also find the following message in the job execution log:

Can't open data connection for transfer of "<path-to-remote-file>" (425).

This problem can be solved by switching to FTP passive mode. To do this just open the job where you receive this error, find the FTP destination, and click on the “Edit” button as shown in the picture below:

Then go to the “Advanced FTP settings” and select “PASSIVE (PASV)” in the “Connection mode” menu:

After that, don’t forget to press the “Save & Exit” button to apply all the changes.