Copyright 2002, Rick Macmurchie - October 8, 2002

E-Mail Attachment Safety Update 1

Changes in how Outlook Express 6 handles attachments after installing Service Pack 1 (SP1)

Please read the original article E-Mail Attachment Safety for basic information about safe email use before reading this article.

Outlook Express 6 Service Pack 1

All versions of Outlook Express before version 6 Service Pack 1 handled email file attachments (by default) in an unsafe way. That is to say that even if you had all of the security updates installed it would still let you open an executable file attachment that could be dangerous, containing a virus, worm, or Trojan horse.

Starting with Service Pack 1 for Outlook Express 6 that has changed, the default settings in SP1 is now to block access to potentially dangerous file types. Unfortunately I have not been able to find a list of the types of files that are blocked, but I have noticed that it tends to block access to some file types that I would consider safe.

On my test system it blocked access to Zip archives (.ZIP) and Adobe Acrobat files (.PDF), both are files types that are very commonly mailed file formats and that are reasonably safe. (See my article about Zip files)

The following boxed text is from an article on the Microsoft web site that describes how to allow access to some blocked file types.

NOTE: The Internet Explorer 6 unsafe file list includes any file types that may have script or code associated with them. To add additional file types to be blocked or remove file types that should not be blocked:
  1. Click Start, point to Settings (or click Control Panel), and then click Control Panel (or switch to Classic View or View All Control Panel Options).
  2. Double-click Folder Options.
  3. On the File Types tab, click to select the file type that you want to block or allow, and then click Advanced. If the file type you want to add is not listed, perform the following steps:
    1. Click New.
    2. In the Create New Extension dialog box, type the file extension you want to add to the unsafe file list.
    3. Click OK, and then click Advanced.
  4. Click to place a check mark (block) or remove the check mark (allow) from the Confirm open after download checkbox.

NOTE: You cannot remove the check from Confirm open after download to allow some file types. For example, .exe files are in the default unsafe file list in Internet Explorer and cannot be allowed.

I tried to use this method to restore access to ZIP and PDF attachments, but Outlook Express would still not allow access to ZIP or PDF files after making the above described change.

Allowing Access to blocked file types

You may find that you need to open or save a file that has been blocked, ZIP and PDF files in particular. If you need to open of save an attachment that has been blocked you can turn off the blocking feature.

To disable the blocking feature:Screen Shot showing where to uncheck 'Do not allow attachments to be saved or opened that could potentially be a virus.'

  1. Click Options on the Outlook Express Tools menu.

  2. Click the Security Tab.

  3. Remove the check mark beside 'Do not allow attachments to be saved or opened that could potentially be a virus.'

  4. Click OK

You will now be able to open or save any attachment. Select and save the attachment that you needed to access and then turn the attachment blocking on again.

Never open of save a file with an extension listed in the dangerous file extensions list in my original article about E-Mail Attachment Safety!

An alternative to disabling the blocking is to arrange with the sender of blocked file types to rename the files before attaching them. For example a ZIP file renamed to end with .ZI would not be blocked, you would be able to save the file and add the P back to the end of the file name.

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Rick Macmurchie
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