Evolution is a mail manager that is very similar to the almighty Outlook (one of the tools included in the Microsoft Office pack) both in terms of aspect and functions. The program has a section with which to manage the mail, an address book for your contacts, various calendars, a task following system and a utility to take notes.
Professional and totally free email manager
The tool offers exceptional performance and some really practical functions like an integrated search engine, compatibility with vCards, task lists, integration with Microsoft Exchange and Collaboration Server, synchronization with web calendars, customized reminders and integrated security and filtering system.
It is probably the open-source mail manager that looks the most like Outlook, something that makes it optimum for a work environment, due to how simple it is to handle and the options that it offers the user.