@silverpill I checked this and according to this list https://the-federation.info/platform/44, https://relay-ap.nobigtech.es/ is using a very old version 0.1 released 2 years ago. I have tried with a relay that uses the latest version 0.3.1 released a month ago, https://relay.21314.de/, and it does the same error, so it seems like a pleroma relay problem that hasn't implanted required outbox property @Tadano