Re: [imapext] offline mode, was Re: [ietf-smtp] Fwd: Request to form a new WG: JMAP

Brandon Long <> Tue, 22 November 2016 05:38 UTC

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From: Brandon Long <>
Date: Mon, 21 Nov 2016 21:38:11 -0800
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To: Tony Finch <>
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Subject: Re: [imapext] offline mode, was Re: [ietf-smtp] Fwd: Request to form a new WG: JMAP
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I've said this to some client developers directly, but it's good to share
the concept more widely:

There should be no "full mirror" clients, only disconnected state clients
which make different choices of window size.  There are Gmail accounts
today which would exceed the ssd in many laptops, or the monthly bandwidth
allotment of some broadband customers.  A full sync is useful for backups,
but a regular client would be wise to make full sync a special case of
"reasonable cache space on this device/connection happens to be larger than
the user's account".

Granted, I would also argue against connected clients in general, since the
next billion users typically have poor/expensive connections, and many
users are on mobile networks where the quality can vary greatly from block
to block.  Network usage is also more likely to be a WAN these days, with
the higher latency that implies.  Also, storage size is mostly to the point
where a local cache can be fairly large compared to most content... OTOH,
shared computers may make local sync or install less desirable, but I think
most of those cases tend to web clients these days.


On Tue, Nov 15, 2016 at 4:10 AM, Tony Finch <> wrote:

> Is everyone here using the term "offline mode" to mean the same thing?
> RFC 1733 defines "offline mode" to mean POP3-style delete-from-server.
> "Disconnected mode" is the term for a client that has a local cache
> or mirror of what is on the server.
> Approxomately no-one wants RFC 1733 offline mode. (Bah, the number of
> times I have had to recover mail for someone who accidentally pointed an
> offline-mode client at their account.)
> How much do the necessary protocol features differ between a full-fat
> disconnected mode client (a mirror on the client of the entire
> account on the server) vs a poorly-connected mobile client which needs to
> sync a smaller window on the account? Concurrent access to multiple
> mailboxes? what else?
> Tony.
> --
> f.anthony.n.finch  <>  -  I xn--zr8h
> punycode
> Trafalgar: Easterly or northeasterly 5 or 6, occasionally 4 at first, but
> 6 to
> gale 8 in southeast. Moderate or rough. Fair. Good.
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