Outlook Express is installed for free by default with Windows and thus, it’s a common default choice among people new to the Internet and Email. Outlook Express does the basics of what an email client must do, but that’s the extent of its scope. You can have multiple email accounts, but all of your email drops into the same folder. To get around this, you can use rules to forward your email to other folders based on the “To” address. It does nothing for spam or phishing scams, and the extent of its security measures is the fact that it doesn’t auto-download embedded images.
Mozilla Thunderbird is another free email client, but it does a lot more than Outlook Express. It has a built-in spam filter, which learns over time what a person considers spam based on what they flag as spam. It is aware of spam assassin headers and can be configured to trust spam assassin’s headers. Between the two, it catches nearly all spam and gets better over time as it continues to analyze new spam email.
Thunderbird also has a phishing detection feature, where it will notify you if it thinks the email is a phishing scam. Phishing essentially is the attempt to mislead somebody into thinking they are going to a particular site, when in fact, they are going to a scammer’s site. Typically, phishing scams revolve around getting people to mistakenly put in their username and password, which is saved so that the scam artist can then log into their real account and gather personal information. This is a crucial feature for those new to the Internet as that warning can save a person from having their identity or credit card information stolen. Most people that have been on the Internet for a while can spot a scam. One such trick is to move your mouse over the link and look at where it’s really going in the status bar. If the address doesn’t match up to the real website, then it’s probably a scam. For example, if somebody wants you to log into “Paypal”, and the address is really going to www.paypal.com.someothersite.com, then it’s a scam.
Thunderbird can use multiple inboxes for each email address that you use, and it has a rules system that is at least as good as Outlook Express. It also allows you to set up RSS folders to take advantage of syndicated content on the Internet from your chosen sites.
As far as email is concerned, Mozilla has it covered.
The only drawback to using Thunderbird exclusively is that it doesn’t have a built in calendar & meeting system like you can get with Microsoft Outlook (the full version, not Express) and Exchange. There are calendar plugins, but to my knowledge, there isn’t a server available that will manage a shared calendar between many people like you can get with Exchange. If you know of such a system, please write a comment as I’d love to use it.
Bottom line, the best free email client available is Mozilla Thunderbird. If you need the ability to schedule meetings, then Microsoft Outlook with an Exchange server is probably the best option; however, Outlook and Exchange are not free. The prices vary depending on how many people you need and how you purchase Outlook such as by itself or inside Microsoft Office, but a small office will typically spend a few thousand dollars in licensing and setup fees.