Backup and restore the Outlook’s RoamCache folder
I’m inspecting my disk about what I should include in my backup and came across the RoamCache folder in a folder where Outlook stores various other files as well.
Inside it, there are a lot of “Stream” files like Stream_Autocomplete_*, Stream_Calendar_* and Stream_CategoryList_*
What exactly is being stored in these files and should I include this folder in my backups?
If so, can I also restore it on another computer?
In short, the RoamCache folder contains an extracted cache of (list) properties and settings which are stored within the mailbox itself.
You do not have to include it in your backups.
Location of the RoamCache folder
By default, the RoamCache folder is stored in the following location:
C:\Users\%username%\AppData\Local\Microsoft\Outlook\RoamCache
You can paste the path mentioned above in the Address Bar of Explorer to quickly open the location.
Extracted cached content and lists
More and more properties and settings are stored within the mailbox. The benefit of this is that you maintain much of your Outlook settings even when you move between computers.
This not only applies to backup and restore scenarios (for POP3 accounts) but also when you have an Exchange account and use that on multiple PCs with Outlook and, for some features, even in OWA.
These properties and settings are stored as hidden messages. Sometimes the data is compressed or encoded in a very specific way. These properties are extracted to the RoamCache folder on a disk for performance reasons so it wouldn't have to query the mailbox itself and extract it from there each time.
For instance, addresses to which you've sent an email before. This belongs to the AutoComplete feature which stores the actual cache in the mailbox itself and no longer in a separate nk2-file (since Outlook 2010).
The RoamCache folder contains a list of files which mostly contain lists themselves.
No need to backup the RoamCache folder
As mentioned before, you don't have to include this in your backups as it can't be restored in a useful way anyway.
When you empty the folder, Outlook will automatically rebuild this cache from the information stored within the mailbox itself.
Restoring the folder to a computer with a new or restored mailbox will not cause Outlook to import or even re-use the recovered files; The files are useless to Outlook.
However, an exception exists for the Stream_AutoComple_* file. When you use the NK2Edit application by NirSoft, you can recover the contents of the AutoComplete cache and even import it back into Outlook. Outlook will then of course build a new Stream_AutoComple_* file but will contain the contents of the old file as well.
Note: For an overview of other files and folder which Outlook uses to store content and settings in and whether or not you should include it in your backups see the Files and Settings guide for Outlook.
