Outlook 2011: where are mail message in my archive file stored?

Outlook 2011 for MAC stores only the indices in a database file and stores the data records (individual emails) as a series of files nested within folders. The Database file and its folders are located here:

~/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Database ~/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records

Adding these path's to your backup strategy should address your issue.

Try this, it explains it quite well. http://www.arxnetworks.com/news/tag/backup-emails-in-outlook-for-mac/

Since there is more than one way doing this: here is an alternative that might suit you better.

In the Category create a Archive (if it is not there already).

When reading a email that you want to archive click on the category and select archive.

In the File menu select Export!

Looks like this:

That will make a file where you want it containing only archived emails.

Drawback--> you can not keep adding new emails to the same archived file.