Very fast and responsive. The embedded view of the attached pictures is a nice additional feature. Also the 3 panel view provides flexibility and a good overview over your inbox.

I love your ability to manage PDF files with the appropriate permissions to work on any operating system we have, which makes it very useful for any business work sector

Synchronization of all your emails in the cloud. Open Source Community with AGPL license. Fast and easy-to-use webmail interface, add Google and Facebook accounts by logging in more easily with HTTPS security on your IMAP server. Multiplatform in Linux and Windows with PHP servers.