Rainloop — Lightweight Webmail Client
General Information
Rainloop is a lightweight webmail client designed to provide IMAP/SMTP access through a clean browser interface. Unlike full collaboration suites, it doesn’t try to be everything at once — it just delivers webmail that’s fast, easy to deploy, and friendly for users.
It’s popular with admins who want a self-hosted alternative to Roundcube, or simply need a web interface for existing mail servers without the overhead of a large stack.
How It Works
Rainloop runs as a PHP application on a web server. It connects to any IMAP and SMTP backend — typically Postfix/Dovecot or Exchange — and presents mail through its HTML5 interface. It supports multiple accounts, domain-specific configs, and integration with address books.
OAuth support allows sign-ins via Google, Facebook, or custom identity providers. For admins, management is done from a simple web panel where domains, authentication methods, and plugin options are configured. TLS is supported natively for secure connections.
Functions
| Feature | In practice |
| Platforms | Runs on Linux/Windows servers with Apache/Nginx + PHP |
| Protocols | IMAP, SMTP |
| Webmail | Modern responsive UI, multiple accounts, folders, filters |
| Integration | Contacts, LDAP, OAuth for login |
| Security | TLS/SSL, 2FA via plugins, encrypted password storage |
| Administration | Web-based admin panel, per-domain settings |
| Extensibility | Plugin system for custom features |
| License | AGPL open source |
Installation Guide
1. Prepare a web server with PHP and MySQL/MariaDB (optional for contacts).
2. Download the Rainloop package from the official site.
3. Extract into the web root and set correct file permissions.
4. Access the /admin panel in a browser and set the admin password.
5. Configure domains, IMAP/SMTP servers, and TLS.
6. Add user accounts or enable automatic login with IMAP credentials.
Most admins run Rainloop behind Nginx with TLS via Let’s Encrypt.
Everyday Use
– Hosting providers deploy Rainloop as the default webmail for customer domains.
– Small businesses use it as a lightweight alternative to Roundcube.
– Internal IT teams provide Rainloop to staff for occasional browser-based access while keeping IMAP as the main protocol.
– Users with multiple accounts benefit from its ability to manage several inboxes in one interface.
Day to day, it’s mostly used for quick access: check mail, reply, manage folders.
Limitations
– It is only a webmail client — no calendar, contacts sync (beyond local address book), or document editing.
– Development pace has slowed in recent years.
– Some plugins are community-driven and may lack long-term support.
– Compared to Roundcube, the ecosystem and user community are smaller.
Comparison
| Tool | Platforms | Strengths | Best Fit |
| Rainloop | Web/PHP | Lightweight, clean UI, multi-account | Hosters, SMBs needing simple webmail |
| Roundcube | Web/PHP | Mature, larger ecosystem, plugins | Standard choice for many hosting panels |
| Afterlogic WebMail Lite | Web/PHP | Similar lightweight approach | SMBs, small providers |
| Horde Groupware | Web/PHP | Broader features (calendar, tasks) | Orgs needing more than mail |
| SOGo | Linux | Full groupware, Outlook sync | Teams requiring calendar + ActiveSync |
Notes from the Field
Admins note that Rainloop’s biggest strength is simplicity: unzip, configure IMAP, and it’s usable within minutes. Users like the clean UI and speed compared to older webmail tools. The main caution is to keep an eye on updates — since development isn’t as active, applying security patches quickly is important. For many setups, though, it’s “set it and forget it” webmail.