I already posted some time ago the problem of not beeing able to copy/paste some simple information like a piece of spreadsheet from Excel (on a PC or Mac).
I suppose there are some problems with the way information is retained in memory, and the way of implement it to be able to paste it in the brower edit page.
Testing the last Office 2008 for mac, I came across an interesting feature : "Paste as image". This let the mac Entourage user past a piece of information like it's an image, so as you may think, the table appears correctly, the cells, and everything on.
I teste copy pasting tables (Excel, Numbers, etc.) to various mail clients like Apple Mail, Entourage, Outlook, Thunderbird, etc...
Only on Windows Outlook was able to get properly the Excel table, the rest was a no go.
Maybe this option could be interesting to implement in Zimbra, and not too dificult without recoding the editor. I don't know for the rest of us, but copy pasting excel sheets are a MUST here...
Oh and by the way, when is that drag&drop firefox plugin comming out ?