Just a FYI in case anyone else runs into this problem.

PS: If anyone from Vodafone/Ihug happens to read this please fix! 

vserve7.ihug.co.nz aka recently appeared on several anti spam blacklists

It appears vodafone/ihug uses these blacklists themselves to filter email before it's delivered to mailboxes on vodafone/ihug email hosting.

This means an email from a fairly straight foward php order form on a small business website on vodafone/ihug hosting sent to the sales address for the website's domain never arrives.  Not tagged as junk and put in the junk mail folder, straight up blocked never arrives in the inbox.

I wonder if this is the definition of irony?

Anyway adding a bunch of other email addresses from various hosts (gmail, hotmail, etc) to the BCC for the email sent as a test shows that most email hosts are marking anything from the mailsever as junk and throwing in their spam folder (at least they don't block it outright like vodafone/ihug).

Good times!