Roundcube

A browser based webmail client that connects to your existing IMAP and SMTP servers, so users read and send mail from any device without a desktop client installed. It includes a message list, contact book, folder management, filters with Sieve support on the server, attachment handling and a large plugin ecosystem for calendars and contact sync.

Organisations and homelabs use it as the front end to their own mail server, giving colleagues a familiar interface over mailboxes they control.

Installed alongside your mail store, the webmail tier adds no vendor account per user, and restoring the whole thing means backing up the mail directory and its configuration.