Microsoft Outlook Express 6.0 

Outlook Express is an e-mail client plus NNTP newsreader bundled with the Windows and IE. It's commonly mistaken as a stripped version of Microsoft Outlook, even though both are distinct platforms and totally different. Outlook Express has earned the reputation of being a worm and virus magnet, and it is so because of its minimum attentiveness towards privacy and security concerns of the user. Outlook's ability to execute JavaScript and display remote images is the root of many of its current security and privacy issues. In the automatic spam-filtering test, this client scored a big zero as it completely relies on the user to set filters for handling spam. Standard elements like a folder list for organizing mail, a contact list, and a preview pane that you can toggle on and off make its multi-paned interface simple. And even though Outlook happens to have the least to offer and worst to perform among all others, it hogs the maximum amount of memory even when idle on the computer.

Among the relative good features, it has a comprehensive mailbox search engine and a detailed address book.