Mobile web browser
Accessing Zimbra through a Mobile Web Browser
All devices with an HTML-compatible web browser can access Zimbra email, contacts, calendar, and briefcase using the Zimbra Mobile Web Client. This is available to both users of the free Open Source Edition and all paid editions.
To use the Zimbra Mobile Web Client, open the HTML-compatible browser on your phone and type in the same URL that you do to access Zimbra in a desktop web browser then add /m/ at the end of the URL.
Be sure to double check if you need to use "http://" or "https://".