Native web-based email platforms are used by millions of users but some of us prefer an OS-specific native desktop application for the same. Generally, these applications support multiple email services and allow you to manage all your accounts from a single location. If you prefer the same, you can select one of these powerful applications to tame all your inboxes from a central hub. Most of the email clients have a beautiful interface and often supports plugins to 
1. Nylas N1: This is one of my preferred desktop email clients I recommend to my peers and friends. Its minimal and clear interface makes email communication, a breeze. It supports all the popular email platforms like Gmail, Yahoo!, and iCloud and works seamlessly on Windows, Linux, and Mac systems.
Its extensible plugin architecture allows developers to add cutting-edge features to the parent client. A unified inbox allows you to combine multiple email streams from different platforms into a single location. Through plugins, you can add contact cards and can detect phishing attempts too. Translation extensions are also available for this email client. It's completely free and is open sourced on GitHub.
2. eM Client: Windows users can try this flexible and powerful email client which supports almost every widely used email service. It can run on almost all popular Windows variants going back up to Windows XP. It's import feature allows you to pull emails and contacts from different 3rd party email clients.
It has complete support for touch gestures and works seamlessly with touch-enabled tablets and laptops. Mail search is also extremely fast enabling you to mine out select emails from a large archive. This email client also allows configuration of custom rules which can be applied to incoming emails with a support of a rich signature for outgoing emails. It also has a built-in spell checker for sending error-free emails.
3. Mailbird: This is yet another powerful and user-friendly email client built exclusively for Windows platform. It's packed with several unique and intuitive features like WhatsApp integration. It comes with several pre-built themes and flexible layout customizations to match with your preference and taste.
Its touch support interface enables an end user to swiftly process emails on a mobile device too. It comes in over a dozen languages out-of-the-box. Power users can also integrate both task management and popular messaging apps with this email client. Multiple accounts can be managed quite easily through its unified inbox. It also has a calendar integration to keep up with your busy schedule and commitments.
4. Opera Mail: This much popular email client is lightweight and is extremely customizable. It has labeling and message filtering support to easily manage and search important email communications. Through its user-friendly tabbed interface, you can open multiple email messages at the same time.
Threaded message view helps you in easily visualizing a long conversation without messing with a chain of emails related to one another. Power users can also create custom sorting rules for the emails to keep the most important messages, accessible. It also includes a powerful RSS feed reader so that you can keep up with your favorite websites and blogs without ever leaving the email management application.
5. Thunderbird: This popular and extremely flexible email client is developed by Mozilla. It's one of the few email clients I've used on my older Windows systems for the last few years. It's updated on a regular basis and is available in different popular languages. It also has a large support community for novices.
Adding contacts to its address book is dead simple with a one-click process. It also has a smart attachment reminder to ensure you do not regret it after sending an important business email without necessary attachments. It also integrates several popular chat networks which are directly accessible from the email client's interface. It has one of the best search and filtering tools for a large archive.
6. i.Scribe: This blazing fast email client can run on almost every popular desktop operating system. It has one of the best spam filtering module which blocks even the smartest spam campaigns. It's a portable client which can be easily used from a USB stick as well enabling you to carry it everywhere.
It comes in over a dozen popular languages and is regularly updated to provide fixes and new features. Power users can write their own plugins for this flexible email client to extend its features. It supports several email and contact formats to enable easy import and export of your important email data to and from external email clients. It also has SSL support including an integrated calendar module for users.
7. Postbox: This classy email client is available both for Mac and Windows platform. If you regularly share confidential or large attachments through an email, this client has a support of cloud storage attachments to ease the entire sharing process. The interface is soothing to eyes and works seamlessly.
It also has support for canned responses which can be instantly activated through a keyboard shortcut. Custom email signatures can also be added at will. Its powerful time-tracking feature calculates writing time as well as the number of words written so far. It also enables quick unsubscription from marketing emails to keep your inbox clean and free from unnecessary junk. Rich contact cards display vital details.
8. Inky: Do try this promising email client you can easily run on Windows, Mac, iOS and Android platforms. Its cloud syncing feature enables you to access the account on different devices without any hassle. Multiple email accounts from various services can be added to manage all of them at one place.
Its smart sorting feature lets you arrange emails based on their relevance which enables you to process important and related emails in an easy manner. Its unified interface presents the same controls and user experience on every single device you're using it. Its strong encryption keeps your email data safe and secure from hackers. Its smart suggestion feature recommends important contacts for an email.
9. Claws Mail: This free and flexible email client is ideal for everyday email communication. It supports threaded display for long email conversations. It also includes color labels for easily segregating different types of emails. It has full-fledged plugin support system to quickly add extra features to the email client.
Like other professional email clients, this one also supports multiple email accounts with filtering support for easy retrieval of messages from old archives. You can also tag and watch select threaded communications so that you do not miss important business information. It also has a powerful dynamic email signature feature for professionals. Drag and drop support enables easy movement of messages.
10. Foxmail: This email client has a nice interface which makes it stand apart from the rest. It has an attachment preview feature to quickly check the contents. It also has a unique delayed sending feature for up to a minute to give you enough time to reconsider canceling a critical business or personal email.
Its contact module can seamlessly merge duplicate contacts and can display an indexed list of the same for easy access. Message search is powered by fuzzy logic which gives instant context-sensitive results. It also allows import of data from Google calendar. It is one of the few email clients which shows related emails. All the folders are sorted automatically and the favorites folder can be customized as well.
11. EmailTray: This intuitive and feature-packed email client is worth giving a try. Users get both visual and audible new email alerts from the taskbar, if enabled. Rich business cards of contacts ensure you get all the information about the recipient at a glance. Rich text HTML emails can also be composed easily.
Password protection for email database prevents unauthorized access on shared computers. Custom email rules are often used by power users to speed up email processing on an automated basis. It can also sense and recover legitimate emails mistakenly sent to the spam folder. Alerts can also be configured for important emails only including unread counts for different groups based on priority.
12. IncrediMail: If you like to jazz up your personal emails, then this email client is made just for you. It's packed with several features to create visually appealing emails. It enables insertion of rich background images and textures within an email body to give a nice and a unique look to the message.
It can also be used to add emotion icons and animated characters at will making the email lively and interactive. This also facilitates sending of custom animated ecards to your loved ones right from within the email client. It can also create a collage of photos which can be used as an email background in different templates. I liked its animated email notifiers which pop up on the arrival of a new message.
13. The Bat!: This email client is made for Windows users with some useful features to manage your email inbox easily. Its dual encryption process keeps your email communication absolutely secure. One can use unlimited numbers of email accounts with this client with no restrictions on the features.
Users can easily send encrypted key-based emails through this client. It can also handle unsafe attachments to keep your system clean and uninfected. It also includes several common email templates which can be used on a daily basis to speed up your email processing routine. Its premium version also supports unique biometric authentication system for added security preventing unauthorized access.
14. Mailplane: If you're an avid user of Google's Gmail service, do try this feature-packed client made specifically for this popular email platform. Multiple Gmail accounts can be processed through a simple and user-friendly tabbed interface. All Apple keyboard shortcuts work with this client out-of-the-box.
Its notification system is directly integrated with the Mac bar which displays an unread count of new emails. You can also disable the notification system if required. Image attachments are inserted easily through a large file dropping zone. Email attachments can also be previewed and can also be annotated through your favorite Mac app right from within the email client. It also has app extensions support.
15. Zimbra Desktop: This email client for Windows platform deserves a mention in this list. It has multi-account support with no limitations on the number of accounts you can use it. A task and a contact manager are integrated with this email client which makes it an ideal choice for professionals.
Its email search engine has an advanced feature which enables its users to quickly filter select messages matching with their query parameters. It also has a mini-calendar application with complete drag 'n' drop support. Plugins are also supported by this client which can be used to integrate custom features and functions. The interface itself is fully customizable to facilitate easy and quick email management.
16. Polymail: This impressive email client has a stunning interface and can run both on a desktop and on a mobile device. It has several unique features that can save your time by many folds. It works seamlessly with all the popular email platforms generally used by professionals and freelancers across the globe.
Its inbuilt tracking feature instantly informs you whenever the sent email is opened at the recipient's end. Similarly, scheduling option enables you to easily send important emails at the right time. Email snoozing ensures you can focus on the important emails first and get timely reminders for less important messages at a later time. It also has a handy unsend feature to cancel the delivery of an important email.
17. MailMate: And last but not the least, this lightweight email client specifically made for Mac platform is definitely worth giving a try. It has full Markdown support for composing rich emails. Through its advanced search, you can look for information both in the email body as well as in the email header.
It has a rich email notification system which is tightly integrated with the operating system. Smart inboxes ensure you get the right email in the desired section for easy processing. Even if your internet connection is down, this email client works quietly in offline mode. Its layout can also be changed for both normal and wide-screen monitors. Keyboard shortcuts for email signatures can also be used.