I used to use Thunderbird Portable for my email. It was nice, but not every computer I interacted with allowed me to load even a portable app. Additionally, some companies block services like gmail. Having a self-hosted web-based email client is a godsend. I can check ALL of my emails (and I have far too many) from a single client.

I like the graphical interface to send and receive emails, different themes available, and languages for the entire email system. Synchronize different email and server services.

Rainloop has not given me any glitches. I have read and sent emails without any hickups. The emails are sent and they reach the recipient every time. It is very easy to use. Not complex or messy interface. Just a great system for sending and receiving emails.