OWA Offline Access via HTML 5

By Serdar Yegulalp, SearchExchange [Published May 2013]

As HTML 5 matures and becomes a fully supported standard on almost every platform, some of its more exotic and powerful features are becoming more widely exploited. Among them is offline storage, which allows an HTML 5 page to work with the browser to store data without a network connection. If this sounds like cookies, you're partly right; it's actually an expansion of that functionality.

OWA 2013 supports offline access in Web browsers that support such functionality for the following programs:

• Internet Explorer 10 (the Modern UI version of IE)
• Safari 5 or greater
• Chrome version 16 or greater

When offline, the user can see his inbox, drafts folder, any folder he viewed through the browser in the last seven days and up to either three days or 150 items worth of content in each folder (whichever is greater). The full contact repository is also available.

This said, you should understand that there are several caveats with using OWA 2013 offline access in HTML 5. For one, attachments aren't available -- period. Calendars provide users with notifications, but multiple calendars aren't available. Additionally, email moves and searches are not available offline.

Users are also not allowed the aforementioned "wide" and "narrow" mode views in offline mode. Note that with Safari, the only platform supported for offline access is the Mac desktop; iOS devices are not supported.

The biggest caveat may be the fact that all information stored in offline mode is cached in an unencrypted format. This is crucial if your user's device does not encrypt storage by default; one can't realistically expect the browser to do that for you. Since one of the things you can do in offline mode is compose IRM-protected messages, you may to ensure that devices that work with OWA in offline mode have on-disk encryption for further security.