[eluser]smidiod[/eluser]
Tricky to explain, but here goes.
With Postfix (default on a Matrix Centos appliance server) I can send from and receive email as normal, but CI's mails get mangled.
With Sendmail - and Exim - (both installed later) I can only send but CI's outgoing mails are received untouched and as I intended them.
Unfortunately, I need to send and receive mail on this server... perhaps there's something in the Postfix configuration that can be altered to stop it messing with CI's mails?
p.s.
When Exim/Sendmail are running they fail to bind to 25 to listen for incoming messages: I have no idea why. If I can fix this, I can bin Postfix and we're good to go. However, this appears to be a bit of a gotcha for other users if they don't have the option. I'm fortunate enough to have a dedicated server on this project.