At Sirius we have recently started using and deploying Roundcube in favour of the tried and tested (but very old) Squirrelmail. Impressed by it's beautiful front-end, ease of use and obvious extensibility, Tom Callway spoke to Till Klampaeckel and Thomas Bruederli, two of Roundcube's core developers, to find out more about this exciting project.

1) What is Roundcube?

Roundcube is a free open source webmail client with an application-like user interface. Roundcube provides all the functionality one expects from an e-mail program and connects to any mail server backend that supports IMAP.

2) To the best of your knowledge where is the biggest deployment to date?

Below are a couple use-cases, which we'll probably put on the website as well some time soon. All people of those people are active in one way or another on our mailing list, [email protected] and [email protected] and agreed to share more experiences and help users in case they have questions.

Most of these installations also have another alternative to RoundCube (e.g. Squirrelmail or Horde/IMP)

University of Michigan
users: 70,013 (there are more users, but the others haven't used Roundcube yet)

XS4ALL, Netherlands
users: 50,000
users: 3,500

San Pablo CEU University (Spain)
users: 15,000+

users: 5000 active users

3) How does Roundcube differ from other open source webmail solutions?

For starters, Roundcube looks awesome! :-)


Thanks to its ajax-based architecture it's fast and responsive and it's used just like a "real" (desktop) application.

Another big advantage is the separation of the frontend from the functionality which makes Roundcube fully customizable using the skins. We learned that a lot of people want more options when it comes to customizing the visual appearance than just choosing from different set of colors.

4) How extensible is Roundcube using its plugin API?

Plugins are very easy to develop due to their object-oriented architecture. Roundcube is shipped with a couple simple plugins which can be used as template to get started.

Roundcube's core currently offers over 40 plugin hooks and we try to please everyone by implementing requests for new plugin hooks right away.

Roundcube's API provides hooks for both the server and the client side. Add the JQuery library (for client side scripting) to the mix and it's even easier to extend the client functionality because so many developers are already familiar with it.

5) Roundcube is built on IlohaMail's IMAP library. Why did you choose this as the underlying engine?

At the time when we started Roundcube, the IMAP library was not a default part of PHP and we wanted to provide a software that runs on any standard Apache+PHP box without lots of dependencies. The Ilohamail IMAP wrapper seemed to be simple and also faster.

6) Do you have ambitions to extend Roundcube to offer a groupware functionality like calendaring in the core application?

No, we personally don't have such ambitions but the plugin API should make it possible to extend a Roundcube installation with such features.

There are already other sophisticated open source solutions for groupware and we don't want to compete with them. We'd rather see a couple integrations.

7) Why was it so important to release Roundcube as a free, open source project? What advantages does it bring as opposed to using an 'opencore' business model?

Open source software is a very important part of Roundcube itself and we wanted to contribute something back to the community. The main advantage for us is that the software is provided "as is" and we don't have to provide support or responsibility to our "customers". This may sound a bit rude but all of the core members of the Roundcube team are volunteers working on the project in their spare time. We all have our jobs beside Roundcube and therefore we cannot provide real-time support or immediate fixes if a problem occurs. This is something people would expect when the pay for a product.

8 ) Can users try Roundcube without doing a full installation, to just to get a feeling for the capabilities?

No, we currently don't have an online demo ourselves. But on the Roundcube forums, there are always a couple users who run demo sites.

9) Are you seeing more interest in Roundcube within enterprises with the economic downturn?

When looking at the download counts we don't see an increased interest in Roundcube. Maybe enterprises still hesitate to use open source software. Maybe that's because the IT industry really hasn't seen the crisis (yet).

Also, one of the reasons people always hesitate to use Roundcube are the conservative versioning we keep. Despite what people think - we are currently "only" at zero dot three dot one.

We are pretty sure that this relatively low version number make it look like we are not finished yet.

10) How is your project organised and how might somebody interested in contributing to the codebase get involved?

The core team of Roundcube consists of about 5 people who keep up the infrastructure and control the development process. The most important tools are the Trac platform with the bug tracker and the developers mailing list. This is the place where the ongoing development is discussed and where everybody can contribute. See

11) You've just released version 0.3.1? What features are you most excited about?

The plugin API. It's very exciting to see what people do with it and how they extend Roundcube to become an integral part of their platform.

12) To your mind what does the open source movement need to get even more traction? Better evangelists? Better marketing?

From our perspective the biggest factor are people. It always requires more people who actively contribute to open source projects.

Contribution is not just about writing code. It also includes writing documentation, writing bug reports, answering questions, translating and of course evangelism. Whenever a company decides to integrate open source software for their customers and then encourages their employees to contribute their work to the project, that's a great situation for any open source project to be in. And those are of course the kind of projects any active open source contributor likes to have.

In Roundcube's case some of our contributors are paid by their employer (or a client) to work on Roundcube, but this is currently just a minority.

The original post can be found at Sirius Labs