Anyway, this gets even more interesting, in a way.
I just went onto (oh why the heck not just say it) farmline.com which is when clicked
farming.co.uk
and found a page
http://www.farming-online.co.uk/support/email/which says
"Important Information for senders experiencing rejection errors
The Farming Online e-mail service adheres to all current RFC guidelines/standards for SPF, DKIM, HELO, PTR checks and blacklists to minimise spam for all e-mail users.
This may affect some own domain senders (ie senders using an incorrectly configured exchange server, or sending using a different smtp server address other than the domains own smtp address). "
