Question about Outlook Express

I understand, that the files with extension olk14MsgAttach are files used by Microsoft outlook to handle attachments.  I found them in Documents/Microsoft User Data/ Office 2011 Identities/Main Identity/...

Could something be wrong with those, since I have about 12Gb of those? 
I would like to get rid of them to save space on a crowded disk.

I also have a series of Office 2008 files hanging in a similar place, although I have upgraded to Office 2011 long time ago - can all these files (the directory calle Office 2008 Identities) just be discarded?

thanks