Microsoft Excel cannot open or save any more documents because there is not enough available memory or disk space.

The solution is easy - it's just a stupid error message that has nothing to do with the actual problem, and the problem is actually a microsoft feature, as often is:

- Office now has some kind of "protected-mode" feature, which prevents office apps from doing certain things under certain conditions.

- One of them is to stop excel from opening attachments coming from outlook :-(

Just go in Excel options, trust center, settings, and untick all the options about "protected view".