Back in the days of X.25 and the UK "coloured book" protocols, grey book email went over blue book "network independent FTP" (in batch). I don't know how NIFTP

Back in the days of X.25 and the UK "coloured book" protocols, grey book email went over blue book "network independent FTP" (in batch). I don't know how NIFTP compared with ARPANET FTP as a protocol, though.