What strange email system is PM John Key using then?

Here’s a paragraph from an article in the the Green Left Daily (aka NZ Herald). It relates to the file containing the email messages between Andrea Vance and Peter Dunne. The file was emailed to the Henry inquiry by Parliamentary Services as far back as May 21st.

Parliamentary Services say they almost immediately realised that sending the file was a mistake and tried unsuccessfully to recall it. Instead the email with the file was deleted. No harm was done anyway because-

The head of the Department of Prime Minister and Cabinet Andrew Kibblewhite said the file could not have been opened because the email system was incompatible with that used by DPMC.

What the hell is this? John Key uses a different “email system” to everyone else in government?

Possible, but I doubt it.Why would the PM’s office use a different email system to everyone else? My guess is they would all use MS Outlook/Exchange and the file would have a .pst suffix which could be opened by anyone using that email software, which I reckon they all would be.

I think Kibblewhite’s claim that the email system was “incompatible” is just rubbish.