I don't want to get into an Outlook and Outlook Express argument, But I have used it for years with no problems. I tend to go for Express, as I don't need all the extras of Outlook. If you do Windows Update, Outlook Express is covered.
I am pretty much agnostic about operating systems and hardware. (Note that I did not immediately recommend that Bill switch from IE to Thunderbird.) On the other hand, I don't see the two as being equal from a security perspective. Security bugs for IE and Outlook Express outweigh the number of those for Firebird and Thunderbird--both in number and severity. See
Bugtraq.
On the other hand, I would say that Thunderbird has suffered performance issues versus Outlook Express. Thunderbird has been improving in this aspect.
And if you use the preview, any virus contained in an email stays contained.
Not necessarily true, especially if you use Outlook Express. As far as I know, Outlook Express will still display HTML and remote images in the preview window (I don't have Outlook 7.0). That is, Outlook Express will preview an email much as if it were a webpage. The first security issue with this is that it allows the sender to verify that the email was viewed. This information is important to spammers, who are always looking to verify that each spammed address is in fact a valid and used address. You may not get a virus from a remote image; however, you will likely get more spam. Also, remote images allow any sender to verify that you've "read" an email.
By default, Thunderbird does not display remote images. Also, it is easier to set the display "as text only" in Thunderbird. Displaying emails as "text only" by default provides superior protection against several types of attacks.
The greatest difference, however, lies in the much better protection that Thunderbird provides against
phishing, which is, in my opinion, now a much greater threat than viruses. For those not familiar with phishing, phishing is an attack whereby the attacker sends an email resembling an official email from some type of organization with which the recipient may have a financial relationship. Most common are emails purported to be from Paypal, ebay, and banks. The trick is that the email contains a "click here to login" type of link; however, this link takes the user to the attacker's fake website. If the user logs in, the attacker then gains the user's user name and password.
Thunderbird provides vastly better
anti-phishing protection, including warnings for emails that may be phishing attacks (called "scams" by Thunderbird).
Please note that my comparison concerns Outlook Express and Thunderbird "out of the box" except where noted. Each has settings and add-ons that can improve security.
