Possible Offline Features

This area is for listing all the possible features that an email client might have related to working offline that do not have a user interface component.

• Suspend polling/downloading
• Queue outgoing messages
• Track deletes and other transactions
• Automatically send queued messages and apply pending transactions when online
• Deal gracefully with accounts "offline" due to inaccessibilty (e.g., a work account from home)

External Resources

• Ray Ryan reminds OSAF to have a good offline mode

-- DuckySherwood - 04 Mar 2003

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Greg sez: "The difference between on-line and off-line is the frequency of the polling."

That epigram actually espouses a design paradigm: don't assume that the agent is connected to the archive. It's too easy when using protocols that expect to be continously connected (IMAP, SQL) to execute actions "immediately" (that is, assuming the existence of an active connection). Instead, the design must be careful always to queue up any action and deal with it on the next poll cycle. If a quick response is expected, simply force a poll cycle (which would do nothing if off-line). This would have low overhead if the action actually could piggy-back on a current connection, but still work properly for polled connections (POP, NNTP, RSS).