Scott Hanselman

Unblocking blocked attachments in Outlook

June 01, 2006 Comment on this post [9] Posted in Musings
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My wife emailed me a PST file that she wanted archived to our RAID array. It was easier for her to email it. However, Outlook blocked the attachment because of the PST extension, as it does for many extensions. Some of the blocking I find irritating and a little paranoid.

Here's how to unblock blocked attachments.

(Substitute the appropriate version numbers for your installation, 12 is 2007, 11 is 2003, etc.)

Picture of REGEDIT showing the Registry Key

Add a registry string value under HKEY_CURRENT_USER\Software\Microsoft\Office\<VERSION>\Security called Level1Remove and add the extensions you want with leading dots and trailing semicolons like:


Picture of a message in Outlook with a PST file NOT being blocked

And all is well.

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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June 01, 2006 9:49
Archiving PST files? C'mon Scott - You honestly expect us to believe that you don't run an Exchange server? ;)

Due to the fact that I am constantly switching between four different systems, I'm a Gmail junkie. It provides almost everything I need: A calendar, a smart interface complete with hotkeys, and tons of space. What kills me about Gmail, though, is that they even block compressed files with EXE files in them. See:

I can't say I see the logic in Outlook blocking the PST extension. I was reasonably sure the file format was basically just a database of some kind. Sure, it could carry executables within the messages in the PST, but they'd still have to be viewed via Outlook, which would still block the suspect extensions. It makes me wonder what there is in the spec to make it worthy of being deemed a threat.
June 01, 2006 12:03
Funny you say that. I've thought many times about running an Exchange Server, but I actually have no official "Servers" running in the house anymore. I used to, but while I have a wiring closet, I don't have a server closet. My main PC is my print server, file server/raid, scanner server etc. The closest thing I have is \\media which is video/music.
June 01, 2006 13:52
I've previously had success with the following Outlook addin to allow certain extensions through:

There are others:

Of course, they may not work with the latest version of Outlook.
June 01, 2006 21:50
Oooh, now I can bombard you with my .pst viruses. ;)
June 02, 2006 0:16
One thing to note is that this doesn't work if you are using an Exchange Server. It has to be done at the server, the registry entries seem to be ignored (I've tried!)
June 02, 2006 3:02
Are you running office 12? The outlook screenshot is much cleaner than my default install. If thats not office 12 how did you get it to look like that?
June 03, 2006 20:10
Rename the file extension and leave a note for the recepient to rename it back. That's what I do whenever I email someone an exe or zip.
June 13, 2006 0:46
Couldn't you just have wrapped the file in a .zip file? Or does Outlook scan within archives?

I know that there are certain SMPT servers which restrict attachments to .zip, .jpg and a few other types, so sometimes unblocking on the recepient's side is not sufficent enough for the attachment to go through.
June 13, 2006 8:48
Riker, sure I could have, but:

* I didn't send the file, it was sent to me. I could get folks to change their behavior, but I still needed to get to the file.

* Many servers actually look INSIDE zip files now and strip things out.

Either way, it's a small and easy change that made my life easier.

Comments are closed.

Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.