The best replacement for outlook web app is outlook web access.

The best alternatives to outlook web app are rated as following:
★★★★★  outlook web access
★  outlook anywhere

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Speaking about outlook web app, one probably shouldn't forget about hotmail.

Other search terms related to outlook web app and their ratings are:
★★★★★ hotmail
You have in mind a companion for outlook web app and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of outlook web app in all years. Click on graph for more.
outlook web app
outlook web access
outlook anywhere