This happens automatically for domains that are purchased from our website. All you need to do is specify our name server(s) as a secondary name server. If you apply for this service for an existing domain you can enter the name servers via 'Register name servers'. Remember to give permission to TransIP to execute zone transfers and always increment your serial number when changing anything.
The list should be formatted as follows: a plain text file containing only one domain per line. Comment lines (starting with ; or #) and blank lines are permitted.
You can maintain the .txt yourself or have it generated by a script; in the latter case make sure to forward a Content-Type: text/plain header. Forward the URL to TransIP Support for activation.