Sparrow, the much-beloved email client for Mac and iPhone, was essentially discontinued after it was purchased by Google last summer — but its influence is still being felt. Just take a look at the new Windows-only Gmail app Mailbird, which just became available in a public beta. While the Mailbird team is bringing a few noteworthy things to the table, it's clear the app is heavily influenced by Sparrow.

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Not that that's a bad thing — Mailbird offers a lightweight three-pane interface with your Gmail inbox and labels on the left, a list of conversations in the middle, and full message details on the right. Just like Sparrow, the left column can be shrank to hide labels or expanded to show them, and the right-hand column shows the most recent message (previous messages are compressed). There's also a quick response option for each email, or you can pop open a bigger compose window with more formatting options. Compared to other Windows email clients like the popular third-party option Postbox, Sparrow is definitely a more minimal option.

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Mailbird is pretty obviously inspired by Sparrow, but that's not a bad thing

There are also a few creative additions here — Mailbird includes an "apps" section to let users expand the app's functionality (ala add-ons for Thunderbird or extensions for basically all modern browsers). For example, it lets you search all of the contacts in your email account and pulls in links to Facebook (assuming you log in with your Facebook account, which also pulls in profile photos, just like Sparrow). It doesn't appear to be searching your curated Google contacts, but it still provides a quick way to find an email address you might be looking for. The apps section is open-source, so third-parties can develop and add anything they like. The pickings are slim right now, but the idea of an email add-on system could prove to be quite useful.

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Third-party add-ons could prove to be a notable feature down the line

Unfortunately, there are a few downsides — most notably the fact that Mailbird currently only supports one email account. If you use more than one, you'd have to fully log out and clear all of your account's preferences before adding another one. Furthermore, Mailbird is limited to Gmail accounts, for now — its developers say that multiple accounts and support for email systems besides Gmail will come down the line.

There's also the matter of price. Mailbird will eventually offer a free but ad-supported version that includes a permanent "send from Mailbird" signature, or users can sign up for $12 / year subscription for a "pro" version (you can pre-order Mailbird Pro now for $9 per year). It's not yet fully clear what the Pro version will offer aside from the option to remove the ads and signature. These caveats aside, Mailbird is definitely worth keeping an eye on — it's fast, functional, and could get some useful additional features down the line, both from the developers and its third-party app store.