Jira may be extremely sluggish and require a large amount of memory on the client side.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Roundcube - Web-based IMAP email client
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
Wrike - Wrike is a flexible, scalable, and easy-to-use collaborative work management software that helps high-performance teams organize and accomplish their work. Try it now.