My customer reported that his elderly version of Outlook from MS Office XP (2003) had suddenly stopped downloading email and reporting error 0x8004060c, although it was quite happy to send. This is a known problem with local versions of the app using a .pst file to store data rather than MS Exchange. There is a 2gb limit using older versions of the file and 20gb if using a later format.
Solution; split file by creating (or using) an archive, compact file using in-built tool, start using /or/ create a new .pst file possibly in the later format?