Outlook Secure Temporary File Folder

Symptom – can’t open attachments to emails.

This is one of the things about Micrsoft that will eventually push me over the edge.

A few months back, my CFO called me in to his office saying he couldn’t open attachments from an email in Excel.  I poked around a bit, and as is his wont to do, there were several instances of Excel open, 40 or so outlook items, and various other applications open on his four monitors.  He never reboots, so I assume this is just and Excel memory issue or somesuch, and recommend he reboots at the end of the day.  He does, but it doesn’t work.

I start poking around some more, and low and behold come across the Outlook Secure Temporary File Folder.  This is a little know folder where outlook stores copies of attachments that it needs to open in other applications.  When all is well, this is fine.  Outlook removes the temporary file after the attachments supporting application is closed.  If, however, you exit Outlook WITHOUT closing the supporting application or if Outlook unexpectedly closes, the temp file is NOT deleted.  Again, not normally a problem, but outlook has a limit on the number of files of the same name that it can store.  If you have 99 “orphaned” files in the temp folder whose source attachment have the same name, when you try to open the 100th, you will get an error saying you can not open any attachments.  For example, suppose you get an email every day with a report that is automatically generated.  Call it Daily Report.xls.  If you quit outlook everyday before you close the attachment and do this 99 times, you will have 99 copies of Daily Report in the secure temp folder.  When you attempt to open the attchment on day 100, it will fail.

What to do?

You need to delete all of the files in the secure temp folder.  To do this, you need to find it first ;)

You can look at the MS Article, but the location of the folder is in the registry as below.  Find the folder, delete the files and you are good to go.

Viva la Microsoft!

Thanks to T Mills for giving me the heads up on this.

Outlook 2003

Value Name: OutlookSecureTempFolder

Data Type: REG_SZ

Outlook 2007

Value Name: OutlookSecureTempFolder

Data Type: REG_SZ