Hiri

Fast, good looking email client. Lighter than MS Outlook with some unique and clever features.
You can use Hiri to connect to Exchange, Office365, or a Microsoft email account (Outlook.com, Live, Hotmail). Other email providers, such as Gmail, Yahoo, etc are currently not supported.

Basics:

Fully integrated calendar
Tasks
Contacts
Built for Exchange, Office 365 and Outlook.com
Uses Microsoft’s own protocol – EWS. So if you need to go back to Outlook, everything will be synced.

Nice features:

Great task list built in. You can just drag an email to the right-hand side to make a to-do item out of it.
Super fast search
Triage emails using the Action/FYI filters.
Deal with emails using the 4 D’s – Defer, Delete, Delegate and Do.
Send emails with actions
Dashboard and timer to remind you not to check email too often (this is a really bad habit!)
Nice touch – the subject line is at the bottom of the compose window. You’ll write a better subject line AFTER you’ve written your email. Get your emails noticed.