Microsoft’s online and desktop versions of Outlook have a lot of similarities, differences, as well as some incompatibilities.
Outlook Web Application
The web version of Outlook is best suited for email access when you are away from your primary computer or mobile device. Additionally, there are many settings and features that are only available through the web interface. Under the more settings toolbar, you can view your privacy options, create additional aliases, and set up automated flagging rules.
Some of the features between the web and desktop versions overlap. However, the home user is best off using the web version for a few of these. Some examples include, managing junk mail, email forwarding, and automated vacation replies. These features work best when your email application is always on and the web version meets that criteria. On the other hand, when you turn off your computer, the desktop version of outlook is also off and unable to perform these tasks.
Outlook Desktop Application
The office and windows live versions of outlook are best suited for power users. There are a number of advanced configurations and customizations that are only available in the desktop versions. Here are a few examples:
You can free up the amount of storage used in your online account by moving some of your emails, calendar items, etc. into your computer’s local storage by creating an archive. Once you create an archive, it will show up as just another folder in your navigation pane. However, those items will only be available for viewing on the computer that they were created in. In other words, when you log into the web version of your email account, you will not see the archive folder you created.
- Add-on customizations
A number of developers create add-ons for outlook that extend the user interface and feature set available. If you ever found yourself thinking how much better outlook would be if it had xyz feature, check a search engine to see if someone might have already developed such a feature as an add-on.
- Offline access
The desktop version of outlook lets you compose email, edit your calendar, and view messages that have been locally synced. Any changes you make offline will go into effect once your internet connection is re-enabled. You can also schedule when you want a given email to be sent.
Some incompatibilities exist between the desktop and online versions of outlook. One notable example is creating and managing group contacts as is described in Microsoft’s KB article 2811596 . However, in most of these cases, there are ways to work around these problems.
I advise thinking of these two applications as complimentary. The key thing to understand is that one is not necessarily better than the other. Each version is designed in such a way that one is more ideal than the other depending on the task at hand. Knowing the difference between the two will help you decide which one is best suited for a given task.