I have to say that this is definitely one of the best email/calendar clients that I have found. I initially used Outlook, but found that it was way to slow when dealing with my IMAP accounts and syncing my calendar to GMail. I switched to Thunderbird and was quite happy, especially with the speed of working with my IMAP accounts. It had some downsides though with regard to refreshing my Calendar quite often, which got annoying. I also had an issue where read/deleted emails from other devices were not refreshing correctly in TB.
I went looking again and stumbled upon eM Client. I could not be happier right now. The speed that the app is able to sync accounts and make updates is terrific. It has a very smooth interface and look as well. One additional benefit I found is that I can now sync and download my Microsoft Exchange account, so I can now work with all of my email accounts on my desktop. Previously, I had to use Web Outlook, which meant I couldn’t move things from Exchange to my IMAP accounts and back. I can also see my work Calendar at home and make quick updates as well, which is not easiest when using Web Outlook.
Keep up the great work!