RFC 17:Some Questions Re: HOST-IMP Protocol
RFC-Ref

queue


Click on the red underlined text to get to the source

... message reaches the head of the destination IMP's output queue to the Host (i.e. just before a message is sent to the Host ...
... premature release of the RFNM. The new message will subsequently take its place at the end of the output queue to the Host thus guaranteeing the preservation of the proper message arrival sequence. ...



Google
Web
RFC-Ref