Outlook Attachment Cache:
Name Conflict Issues
Suddenly, 1 or more specific user(s) on a
system running Outlook mysteriously fail to open "seemingly" a
certain type of attachments, and "seemingly" only from a certain
source. What is known: "default application" settings,
as well as
corruption of Outlook itself and/or the application for the intended
attachment have all been ruled out.
This happens under certain circumstances, if the attachments in
question have the same filename. It does not pertain the sender's
platform. Standard behavior of Outlook
- When an attachment is directly opened within a message (as
opposed to saved first), a copy of the file is saved in the Outlook
SecureTemp folder, so that antivirus can scan it.
- The cached copy will be deleted by Outlook,
- if the message is closed (or moved away from reading pane),
while the attachment is still opened (in its application),
- if the attachment is closed first, the cached copy will remain,
even after the message is subsequently closed!
- If there is a name conflict in saving a cached file, Outlook
appends a suffix of (2), (3) and so on, until (99)
- On the 100th conflicting occasion, Outlook will fail to open
such an attachment with the same name.
e.g. photo.jpg photo(2).jpg photo(3).jpg ... photo(99).jpg
- Avoid repeatedly (>100x) using
duplicated filename for attachments
- Avoid the problematic
closing sequence outlined above in #2
- Simply manually empty
which is located within the Temporary Internet Folder (TIF).
Up until 2003, the Outlook SecureTemp folder name is OLK???? (4
random alphanumeric characters). From 2007 on, it is called
Content.Outlook which contains a subfolder named with 8 random
The location of the SecureTemp is stored in the registry and
you can change the path to point to a new location, but be sure the
new folder exists before changing it in the registry,
otherwise you will have red x for images. The
OutlookSecureTempFolder value is at the following
for your version of Outlook.
Note: If the folder does not exist, the key will be reset to a new
OLK* or Content.Outlook folder under Temporary Internet Files.
Hints for Actual Procedure
(entered into W7 search box) will find Content.Outlook
folder among other app temp folders, more will be displayed, if Explorer
is in "show hidden" mode. If that's entered into address bar of
Explorer, it'd display the content of TIF
instead. Typical default locations (many variants, app + os
- %localappdata%\Temporary Internet Files\Content.Outlook
- C:\Documents and Settings\%username%\<randomfoldername>
- test files (set of 99 files) to aid in troubleshooting &