How to Block Customized File Types in Outlook Attachments

By default, Outlook will block some potentially unsafe attachments, like .exe, .com and .bat files. Apart from the preset attachment file types, we can configure Outlook to block other additional ones. This article will teach you step by step.

In our previous article “What to Do If Outlook Blocks Your Email Attachments”, we have discussed about how to release the blocked attachment file types as per our needs. Generally speaking, Outlook is so smart that it can recognize and block various potentially unsafe attachment files. However, sometimes, we may find some additional file types which are also unsafe. Thus we would prefer to add the new attachment files into Outlook blacklist. Here are detailed steps.

Block Customized File Types in Outlook Attachments

  1. At the very outset, head to “Start Menu” and search “regedit”. After that, you ought to press “Enter” key button.Search “regedit” in "Start Menu"
  2. Another new dialog box of “User Account Control” will arise, which is asking you whether allow Registry Editor to makes changes to your computer. Just hit “Yes” button please.User Account Control
  3. Now you will open Registry Editor successfully. Then browse to the following registry keys in sequence: “HKEY_CURRENT_USER” > “Software” > “Microsoft” > “Office” > “14.0” > “Outlook” > “Security”

Note: Here “14.0” stands for Outlook 2010. Your selected number should vary with the Outlook versions. For example, “12.0” refers to “Outlook 2007”; “11.0” means “Outlook 2003”.

  1. When locating “Security” key, you should right click on it. From the right click menu, you need to select “New” > “String Value”.Create a new string value under Security
  2. Next turn to the right pane. Name the newly created value as “Level1Add” and press “Enter” key button.
  3. After that, you have to double click on the new value. In the subsequently popup dialog box of “Edit String”, you can specify its data. As per your needs, in “Value data” field, you can type the file name extensions of the attachments which you want to block. For instance, if you wish to block both .zip and .gif files, you can input “.zip; .gif”.Specify Value Data
  4. Finally you can test it.
  • When you try to send emails containing a .zip file, you will get an alert like the screenshot below:Block Outlook Attachments When Sending
  • If you receive an email which encompasses a .zip file, you will see that the file has been blocked automatically.Block Outlook Attachments in Receiving

Keep Outlook Corruptions at Bay

As is known to regular users, Outlook is susceptible to corruptions. However, if we make adequate precautions, we can reduce the likelihood of the occurrence to a great extent. For example, as suggested in this article, we can block additional attachments which we recognize as unsafe files. Besides, effective relief measures are also badly in need, such as keeping an Outlook recovery tool nearby.

Author Introduction:

Shirley Zhang is a data recovery expert in DataNumen, Inc., which is the world leader in data recovery technologies, including sql recovery and outlook repair software products. For more information visit

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