All open source webmail sucks. Most I have seen are layered on top of IMAP, and IMAP sucks. The reason is you have to have search capability to deal with the high volume of emails nowadays, and it is very hard to do that across IMAP. On the other hand, some other email clients don't suck:
LIV is designed to be self hosted; It is not a SaaS. You run LIV on your own email server with or without an IMAP server. If you don't want to run your own email server please stop right here. If you don't know how to run your email server please do some research first; there are many excellent tutorials out there and this page is not one of them.
LIV is designed for personal usage instead of organisational usage. You run your own email server on your own VPS and your own domain name, serving yourself and maybe a few family members and close friends. To run LIV, you need to have the following setup:
You don't have to have a IMAP server but it may be useful. Once you have a working email setup and you verified you can receive and send email via terminal tools such as mutt you can proceed to the next section.