Frequently Asked Questions
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Q: Why does Outlook Express block my e-mail attachments after installing SP2?

A: Outlook Express now includes higher security features, and because of this higher security certain e-mail attachments that could potentially cause harm to your computer are blocked.

Whenever Outlook Express opens an e-mail that has an attachment, it now calls Attachment Manager to determine if the attachment is safe. The Attachment Manager functionality calculates the risk level of the file, and then compares it to the zone of the file's source. Since e-mail does not have a real source, it uses the Untrusted (E-mail) zone. An API call calculates the zone and appropriate index row in the table. Attachment Manager behavior is determined as shown in the following table:

Risk Level Zones
  Untrusted
(E-mail)		 Internet Intranet Local Trusted
Dirty (Black) -
Example: Virus 		Block Block Block Block Block
High Risk (Red) -
Example: .exe files 		Block Prompt Allow Allow Allow
Moderate/Unknown Risk (Yellow) -
Example: .doc files		 Prompt Prompt Allow Allow Allow
Low Risk (Green) -
Example: .jpg files 		Allow Allow Allow Allow Allow

By default all files start in the Moderate/Unknown Risk row. If the file type matches an entry on a hard coded list of Dangerous file types (such as .exe files), the risk level is moved from Moderate/Unknown to High Risk. If the file type matches an entry on a hard coded list of Safe file types (such as a .jpg file), the risk level is moved from Moderate/Unknown to Low Risk. The following is the Attachment Manager's hard coded list of Safe and Dangerous file types. (Files not covered in the Safe or Dangerous list are initially considered Unknown.)

Safe
  • TXT, TEXT, LOG (only when opened by a trusted handler, such as Microsoft Notepad.)
  • BMP, DIB, EMF, GIF, ICO, JFIF, JPG, JPE, JPEG, PNG, TIF, TIFF, WMF (only when opened by a trusted handler, such as Windows Picture and Fax Viewer.)
  • Trust Logic: Notepad (notepad.exe) and Windows Picture and Fax Viewer (shimgvw.dll) are considered safe when opening their perceived files. This means that if you open a TXT attachment with Notepad, you will not see a trust prompt.
    		•
    Dangerous .ade .hlp .mar .mst .vb
    .adp .hta .mas .ops .vbe
    .app .inf .mat .pcd .vbs
    .asp .ins .mau .pif .vsmacros
    .bas .isp .mav .prf .vss
    .bat .its .maw .prg .vst
    .cer .js .mda .pst .vsw
    .chm .jse .mdb .reg .ws
    .cmd .ksh .mde .scf .wsc
    .com .lnk .mdt .scr .wsf
    .cpl .mad .mdw .sct .wsh
    .crt .maf .mdz .shb
    .csh .mag .msc .shs
    .exe .mam .msi .tmp
    .fxp .maq .msp .url

    In the example of an Outlook Express e-mail, Attachment Manager may take one these actions:

    • If the attachment is clearly safe, it is completely available to you. Safe images are displayed, and safe attached plain text files show as available attachments.

    • If the attachment is clearly unsafe, like a binary executable, it will be blocked: you are not be able to open it at all, but you do see a notice of the blockage.

    • If the attachment may be safe and may be dangerous, you see a warning prompt when attempting to drag, save, open, or print the file. If you accept the option, the file is handled in a way that is guaranteed to trigger any active antivirus program.