Unblock Attachments in Outlook

If you’re using Office 2002 or Office 2003 and you use Outlook as your e-mail client, you may have run into a snag. Outlook classifies many file types as security risks and blocks them. There’s no option you can click or a menu you can check. You can’t download the file.

There are three easy fixes. First, simply use your ISP’s web mail feature to download the file—if it’s still available on your server. Second, the sender can rename the file using an extension that Outlook allows, such as .txt. Then, download it and save it to your hard disk. Don’t try to open it right away. Rename the file using its proper file extension, and then open it. Third, have the sender compress the file using something like PKZip—Outlook likes .zip files, for now. Of course, both you and the sender need the compression software for this to work.

Most of us need Outlook to be a tad more flexible. If you need to receive file types that Outlook blocks, and nothing I mentioned above works for you, change the Registry. Doing so can be risky, so make a backup of your Registry file on removable storage before you change anything. Personally, I’ve never fouled anything up changing the Registry. Just don’t change anything that you’re not 100% sure about and you should be fine.

Now, to unblock specific file types, do the following:

  1. Check Run from the Windows Start menu and type Regedit, and then click OK.
  2. Locate the following key: HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Security (If you’re using Office 2003, the version key is 11.0).
  3. Create a new string value named Level1Remove. You must use that key name.
  4. Open the string value (double-click it) and enter the appropriate file extension you want to unblock. For instance, if you want Outlook to accept Access database files, you’d enter .mdb. If you want to unblock more than one file type, separate each with a semi-colon, as follows: .mdb; .xls.
  5. Close the Registry.
  6. If Outlook is open, close it and relaunch.

Some experts advise you not to leave files permanently unblocked. They recommend that you use this workaround as needed. Once you have the file, you should remove the Level1Remove string value from the Registry. I don’t totally agree. If you're downloading files on a regular basis, constantly modifying the Registry is a nuissance and everytime you change the Registry, you risk making a mistake. In addition, you certainly don't want users messing around in the Registry. Use virus protection software, keep it updated, and don’t open files from anyone you don’t know. However, if you don't need to leave the gate open, don't.

The list of file types that Outlook blocks is extensive. For a complete list search on Attachment File Types Blocked by Outlook in Outlook’s Help.


Susan Sales Harkins is an IT consultant, specializing in desktop solutions. Previously, she was editor in chief for The Cobb Group, the world's largest publisher of technical journals.

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