Since its beta release, Mailbox has been the most popular third-party email client on the iOS App Store.
Users can add up to five Gmail or Google app accounts to their Mailbox account. Swipe messages and them to archive or trash. Scan entire conversations, snooze emails, and get push notifications for new messages.
You can download Mailbox from the App Store here.
Boxer is an email client developed by Taskbox. Similar to Mailbox, users can use swipe gestures to read through new messages. See who your emails are from with profile pictures shown in your inbox. Use “like” to acknowledge a friends message, and use "quick" replies to send common responses while on the go.
Boxer supports Exchange, Gmail, Yahoo, and iCloud.
You can purchase Boxer from the App Store here.
With Google's official Gmail app, users can easily manage and organize their Gmail inbox. Get notified of new mail, see profile pictures as part of the conversation, and read email with threaded conversations.
Organize your mail by archiving, labeling, starring, delete, or report as spam. The new tab system has 5 different categories including primary, social, promotions, updates, and forums. Easily switch between 5 email account. If you don't like the new version, you can always switch back to the classic inbox.
You can download Gmail from the App Store here.
4. Yahoo Mail
Yahoo! Email is an email app developed by Yahoo! Instantly receive notifications for new messages. Scan messages in your inbox and swipe to delete, flag, move, mark as read and more. Attach photos while composing a new message, and preview photos at the top of the message. Auto complete email addresses when you type.
You can download Yahoo! Email from the App Store here.
If you're struggling to keep up with your email accounts inbox, you may want to check out Triage by Southgate Labs. When you login to your email account, new messages will appear as a stack of cards. Flick messages down to keep them in your inbox, or flick messages up to archive. Triage supports Gmail, iCloud Mail accounts, and Yahoo! Mail.
You can purchase Triage from the App Store here.
Dispatch is an email client app for iOS that makes it easy to organize, delegate, and archive your email.
Being a Mailbox competitor, Dispatch has its own unique benefits for those with inbox OCD. The app allows snippets, allows users to respond to emails with common responses, and even customize settings based on the account being used. There is great integration with other third-party apps 1Password, Due, Omifocus, Evernote, and more. For now, the app doesn’t feature push notifications or a unified inbox, which may be a dealbreaker for some.
You can purchase Dispatch from the App Store here.
7. Mail Pilot
Mail Pilot is an app that turns your inbox into a to-do-list. With Mail Pilot, new messages arrive in your inbox as incomplete. When you finish a task, mark the message as complete, and it will automatically be archived by Mail Pilot. Easily collect messages from multiple accounts at once, and manage newsletters, social media notifications, and upcoming events. Mail Pilot works with Gmail, iCloud, AOL, Yahoo, and other email service providers.
You can purchase Mail Pilot from the App Store here.
8. Group Email
Group Email is for users who frequently send...wait for it... group emails! This app makes it very simple to create distribution lists from your contacts, create and send email templates, and easily add photos, videos, and other files from cloud storage services such as Dropbox and SkyDrive.
You can purchase Group Email from the App Store here.
Findit is a very simple file and email searching app that integrates with Gmail, Dropbox, and Google Drive.
Findit uses a very visual and minimal interface to search for items through filters. It can even search through several unique Gmail, Dropbox, and Drive accounts. Hopefully the developer will integrate with more services in future updates.
You can download FindIt from the App Store here.
If you have an MS Office 365 subscription, you have the benefit of downloading and using Microsoft’s OWA app, which brings all of the live panel goodness of Outlook on Windows Phone 8 to the iPhone. OWA for iPhone has all of the inbox and calendar features that are expected from Outlook. If you are an Outlook power user and an Office 365 subscriber, you can download OWA from the App Store here.