[ih] very early email question

[Craig Partridge]

Hi folks:

Strange question.  I've been delving into the history of email and discovered
that the original SNDMSG did not spool messages or seek to retry if a remote
host was down.  It simply returned an error.

So when did email systems start to assume that a remote host being unreachable
was a transient event and save messages for retransmission rather than bouncing
them immediately back to the user?

Anyone know?

Craig

PS: While we're on this general topic.  Another unanswered question.
RFC 354 (first FTP spec that looks like FTP we know) was the product of
an April 1972 meeting in which one of the issues was getting email support
into FTP.  RFC 354 makes clear the idea was to use the APPEND to file
command (which was what SNDMSG used).  Then five weeks later RFC 385
modifies 354 to define MAIL and MLFL in place of APPEND for mail support.
What happened in the five weeks between the two RFCs to cause the sudden
change of approach?