Lost mail with EXPIRE 0 (was Re: [Off Topic] Need review for POP3 extension mechanism)

Randall Gellens wrote:

> >One question about EXPIRE 0 : Am I right that all messages will be
> >deleted after
> >QUIT command. What happens if client disconnects without QUIT? How client can
> >prevent messages from being deleted?
>
> EXPIRE 0 means the server MAY delete messages immediately after QUIT.
> In actual practice, I would expect message expiration to happen later
> in most cases, such as overnight.  The QUIT issue is really no-win.  If
> we say that servers can't delete unless the client sends a QUIT,
> clients will simply not send QUIT (many don't anyway).  And why should
> EXPIRE 0 be different from EXPIRE 1 or EXPIRE 30?

Here I see a problem.
If server will clear mailbox unconditionally when EXPIRE value is zero (i.e.
server will delete even unseen message) it must not advertise EXPIRE 0.
Let's see what may happen otherwise. Client connects to server using dial-up
TCP/IP connection. Client opens mailbox, starts to download mail, but unexpectedly
ISP hangs up modem connection.
Server discovers that connection is lost and deletes mail.

[I ask to forgive my extreme examples, I have mathematical background :-)]

Regards,
Alexey Melnikov
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