[nxjfbwdc] Send large files through email

Send a large file broken up into multiple email messages to avoid maximum attachment size for a single message.  The first step is mail user agents which can break up and reassemble multiple messages of a large file.  (The parts may arrive out of order.)

The second step is a system which avoids exceeding mail account quotas, both the Sent Mail folder and the Inbox folder.  The recipient downloads and deletes messages (out of Inbox) as they arrive and then sends an acknowledgement indicating it is OK for the sender to send more parts of the file.  Analogously, the sender does not send until the receiver says it is OK.

Both sides need to speak SMTP and something like IMAP or POP3.  Integrate if available push notification of a new email arriving (sometimes done by instant messaging from the IMAP server) to avoid polling for new mail.