Comment by aberoham

At least the 'minimum' field in .so's SOA that dictates resolver's nxdomain caching time is only 1200 seconds (20mins) --

  dnsqr ns notion.so
  2 notion.so:
  80 bytes, 1+0+1+0 records, response, nxdomain
  query: 2 notion.so
  authority: so 1199 SOA d.nic.so hostmaster.nic.so 2021021214 21600 3600 604800 1200