Roundcube is an open-source webmail client that lets you read and send email straight from your browser. It connects to your mailbox over IMAP, so you can reach your account from any device without installing anything.
What Is Roundcube?
Roundcube is a web-based email interface written in PHP. It is not a mail server itself; it is a client that connects to an existing mail server over IMAP and SMTP. In other words, it reads incoming mail via IMAP and sends outgoing mail via SMTP. It does inside your browser what a desktop program like Outlook or Thunderbird does on your machine.
The project is free software distributed under the GNU GPL. It aims for a clean, intuitive interface and, with its modern Elastic skin, adapts well to phone and tablet screens. If you want the wider picture first, What Is Webmail? is a good place to start.
What Is Roundcube Used For?
Its core purpose is to give you browser access to an email account. You do not have to install a program: you can open your mailbox from anywhere with an internet connection. The features that stand out in daily use include:
- Managing mail with an inbox, sent items, drafts and custom folders
- Composing, replying to and forwarding messages in plain text or HTML
- Attaching files and previewing incoming attachments
- Building a personal address book and contact groups
- Searching messages by subject and filtering across folders
- Defining multiple identities to send from different addresses
Roundcube is most often delivered as part of a hosting package. For a site owner the practical meaning is simple: you can manage domain-based email accounts (for example contact@yoursite.com) right from the browser.
This is especially handy for a news site or any organization where several team members share the workload. Instead of installing a separate program on everyone's desktop, each person just signs in through the browser. An editor sitting down at a new computer only has to enter an address and password; there is no setup, no synchronization and no profile to migrate. That makes managing email as a team both fast and predictable.
How Does Roundcube Work?
Roundcube is a PHP application running on the server. When you sign in from your browser, it talks to the mail server over standard protocols behind the scenes. The flow looks roughly like this:
- You open the Roundcube address in your browser and enter your email and password.
- Roundcube uses those credentials to connect to the IMAP server and open your mailbox.
- You read, reply to and compose messages; the interface shows them to you.
- When you send a message, Roundcube hands it to the SMTP server for delivery.
- Contacts, preferences and session data are stored in Roundcube's own database.
In this model it is important to remember that your emails live on the IMAP server, not in Roundcube. Roundcube is only the window that lets you view and manage them. Put differently, if you removed Roundcube and put another client in its place, your messages would stay exactly where they are; the only thing that changes is the interface you look through. To see how the underlying services fit together, read Mail Servers: Postfix, Dovecot and Exim.
Installation Requirements
If you want to install Roundcube by hand, the server needs a few components. The table below summarizes the basics; for exact version limits, the project's official documentation is the right reference.
| Component | Role |
|---|---|
| Web server | An HTTP server such as Apache or Nginx |
| PHP | The language the app runs on; certain PHP extensions are required |
| Database | MySQL/MariaDB, PostgreSQL or SQLite |
| IMAP server | To read incoming mail (e.g. Dovecot) |
| SMTP server | To send outgoing mail (e.g. Postfix, Exim) |
Plugins and Customization
One of Roundcube's strengths is its plugin architecture. The core stays lean, and extra capabilities arrive as plugins. Common examples are:
- managesieve: defining server-side, rule-based email filters
- Enigma: signing and encrypting messages with PGP
- password: letting users change their own mail password from the interface
- Extra modules such as calendar, notes and an LDAP-based shared address book
On the presentation side, skins come into play. The Elastic skin adapts to different screen sizes with its responsive design, and organizations can tailor it to their own colors and logos. That way the webmail screen can stay consistent with the organization's overall identity. This flexibility in plugins and skins largely explains why Roundcube is chosen across so many hosting environments: a lean core with a structure that grows to fit the need.
How Roundcube Relates to Control Panels
Most users meet Roundcube not directly but through a hosting control panel. Popular panels usually offer Roundcube as their webmail option: the user creates an email account in the panel and jumps to webmail with a single click.
| Panel | Webmail Approach |
|---|---|
| cPanel | Offers Roundcube as its webmail interface |
| Plesk | Provides Roundcube as a webmail option |
| DirectAdmin | Offers webmail choices including Roundcube |
If you are curious about how panels work in general, What Is cPanel?, What Is Plesk? and What Is DirectAdmin? go into detail.
Strengths and Limits
Roundcube's upsides are that it is open source, light and familiar, extensible through plugins, and ready out of the box in most control panels. On the other hand, it does not have the rich offline capabilities of a desktop client, and its security depends largely on the server that hosts it being configured correctly. It is worth weighing this balance when you decide: the convenience of browser access from anywhere against the fact that server maintenance and updates fall to you or your provider. For most site owners that trade-off is more than reasonable, and Roundcube comfortably covers everyday needs.
- Plus: browser access with nothing to install
- Plus: open source, free and flexible via plugins
- Limit: not designed for lasting offline access
- Limit: security and performance depend on server configuration