Mailbox for iPhone is finally available in the App Store, but don’t expect to use it any time soon.

Unfortunately, Orchestra, the company behind Mailbox, has been swamped with requests to access the app. Mailbox uses a “reservation” system, and they’ll be fulfilling requests on a first-come, first-serve basis. The problem is that, thanks to the amount of coverage the app has received, the number of reservations swelled to more than 341,000 currently. Since Mailbox is handing the reservations at a relatively slow rate, it could be some time before you can actually use Mailbox.

The company published a blog post where they say that the pace of adding users to the app has been intentionally slow.

“Mailbox relies on servers in the cloud to do things like send push notifications, make downloading email as fast as possible and handle snoozed messages," the company said. "Software that is server-based is susceptible to being overloaded, and we want to keep this from happening. ... This [pace] is familiar territory: It’s how many of the services you probably use today (including Gmail) were initially taken to market.”

Mailbox solves some key quirks in the iOS native Mail application and has gotten rave reviews from sites like Gizmodo and the VergeIn the Verge’s review of Mailbox, they talk about how “simple, decisive and logical” the design of the app is. Depending on where and how fast you swipe your finger, navigtaion is easy and efficient, allowing users to delete emails or “snooze” messages that you don’t think are important enough to read now. The purpose of the app is to leave your mailbox uncluttered and without any unread messages.

Unlike Sparrow, another popular email client for iOS that was bought out by Google last year, Mailbox doesn’t have an accompanying desktop app. The only problem is that you might start getting used to using Mailbox to delay your emails until a later time, and you’ll have to defer to your phone in order to do so. Mailbox hasn’t announced whether or not they plan on creating a desktop app in the future.

As of now, Mailbox remains a free app in the iTunes Store, but the company plans on unveiling premium features similar to Evernote or Dropbox in the near future. However, they plan on keeping a free version of Mailbox available even when they release the premium features.

You can sign up for a reservation by downloading the Mailbox app.