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In these days of heightened online security threats, it's a good idea to download and install security updates as soon as software makers release them. Unfortunately, these updates often come with glitches that cause unexpected side effects.

Internet Explorer 6 Service Pack 1, which Microsoft posted late last year, is no exception. Soon after the update appeared (it's also part of Windows XP Service Pack 1), I started receiving letters from readers complaining that IE 6's version of Outlook Express could no longer open certain types of file attachments. This is a safety feature Microsoft added to Outlook Express to stop e-mail viruses--and clueless users--from launching attachments that could infect the PC.

Personally, I think the inability to open file attachments is a limitation we all could live with. Microsoft added the security feature long ago to Outlook 2000 and 2002, and it's never bothered me. I don't need or want to receive as e-mail attachments the kinds of dangerous executable and script files that the feature blocks, and I'm delighted that millions of novice e-mail users can't either. However, if you absolutely must send these kinds of files back and forth (see Microsoft's list of restricted file types), it's easy to override the restriction.

To completely disable file-attachment restrictions in Outlook Express, choose Tools, Options, click the Security tab, uncheck Do not allow attachments to be saved or opened that could potentially be a virus, and finish by clicking OK (see FIGURE 1). Alternatively, you can remove certain individual file types from the restricted list. To do so, open an Explorer window (My Computer, for example), choose Tools, Folder Options, select the File Types tab, locate the file type that you want to remove in the list of registered file types, click the Advanced button, uncheck Confirm open after download, click OK, and then click Close.

If the file type that you want to unblock isn't listed, click the New button, enter the appropriate file extension, click OK, and then modify the Confirm open after download setting as described above. Note, however, that some file types, including .exe and .zip files, can't be unblocked--Outlook Express ignores the settings in the File Types dialog box. To open attachments of those types, you must either use the first technique identified above (disable all file-attachment restrictions) or have the sender rename the file with either a different file extension or none at all.

Stick With Plain Text in Outlook Express

While we're on the subject of safety and Outlook Express, Internet Explorer 6 Service Pack 1 has one more feature that can make OE more secure against mail-borne viruses and Trojan horses.

Flaws in the way Microsoft's mail program automatically renders HTML messages (the ones that have full Web-page graphics and text) allow carefully crafted viruses to launch automatically. But a new feature blocks this automatic rendering; instead it gives you a chance to read the accompanying text-only version of the message (if any) and to open, ignore, or delete the HTML attachment.

To view all incoming e-mail messages as plain text, choose Tools, Options, click the Read tab, check the Read all messages in plain text option under Reading Messages, and click OK.