Mailbird's apps are, to be blunt, pretty lame. They're nothing more than basic Web views for the most part. Calendar, for example, opens the Web-based version of Google Calendar and the Facebook app shows--you guessed it--the Facebook.com website.
Incidentally, Mailbird appears to be incorporate Google Chrome in some way. When I tried out the Google Drive app in Mailbird, the Drive website notified me that I was using an outdated version of Chrome and offered to upgrade my browser. Facebook's security login alerts also notified me I was using Chrome when I logged into Mailbird's Facebook app.
Mailbird performed fairly well in my tests and was very fast at retrieving messages. I only ran into trouble when using the app add-ons. Several times, I had to restart Mailbird when an app froze and once Mailbird crashed on its own when I switched between add-ons in quick succession.
Nevertheless, it's hard to recommend Mailbird in its current beta state. While the software appears to have a bright future ahead of it, the bare-bones service and account support limit Mailbird to Gmail users with a single email address--a major, major drawback.
Even now, however, Mailbird offers a fast, solid no-frills email experience. Power users might be slightly disappointed by the lack of features, but I'm excited to see how the final version shakes out.
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