Outlook online is also offline

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Using Outlook linked to online storage and you keep on working work if disconnected.

Whenever Outlook is connected to online data storage (ie Gmail via IMAP or Exchange Server / Office 365) it will let you keep working if there’s a break in internet access.

Outlook is designed to cache online data into a file on your computer (a PST or OST file) which can be accessed whether or not the computer has a net connection. Outlook switches between online and offline automatically.

That’s why Office Watch has talked about synchronization of data between Outlook and an online data store. The synchronization is done for two reasons:



  • Allow offline access. Outlook can keep working regardless of the network or internet connection.

  • Speed. Searching or reading your email, calendar or contacts is a lot faster reading from a local copy of that information.

While you work, Outlook keeps contact with an Exchange Server/Office 365 machines or IMAP server (for Gmail and others).



  • Any changes online (like new email) are automatically copied to Outlook.

  • Similarly, any changes you make in Outlook (eg mark a message as read, send an email, add an appointment etc. ad nauseum) are copied to the online storage.

If there’s a break in the connection, Outlook will patiently keep trying until the link is restored. You can switch Outlook offline/online but most users don’t bother and just let Outlook figure it out.

Many Outlook users do this, especially corporate users. They read, reply and write emails while offline on a plane – Outlook behaves exactly the same. When they reach the ground and internet access, Outlook reconnects to send the messages and get anything new that arrived while it was at 30,000 feet.

However it’s also great for people with slow or erratic internet connections. Outlook will do what it can, when the connection permits and meantime you keep using Outlook.

Nothing special has to be done. Outlook’s default setup is to turn cached mode on. You can check it from the account advanced settings.

1650 Outlook cached Exchange mode setting - Outlook online is also offline

You could turn Cached Mode off but that would be silly. It would slow down Outlook enormously since every action would have to be checked and retrieved from a remote server. Some corporate systems might force cached mode off when used only on a fast local network and fast server but even that is rare these days,

The initial synchronization between Outlook and a remote server can take a while – if you have gigabytes of data it might take hours. However you can start working almost immediately while Outlook ‘backfills’. When the one-off sync is complete, the ongoing connection doesn’t take long.

Using IMAP you must be cached (that’s what IMAP does).


Whether you use Microsoft technology via Exchange Server / Small Business Server / Office 365 or IMAP (probably using Gmail) the benefits of linking multiple ‘outlets’ to a single online data store are considerable.

With Microsoft’s offerings, there’s nothing really new. Exchange Server has been around for a long time and used by millions of people in organizations around the world. The only difference now is that these ‘enterprise’ features are available to individuals for a surprisingly small annual fee via Office 365.

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