Me again,
Another problem I've found since doing my yum update is that EXIM is now showing the following error, on startup, and repeatedly in main.log
[root@ollie2 ~]# exim -bt localpart@example.com 2016-05-06 09:27:04 WARNING: purging the environment. Suggested action: use keep_environment and add_environment.
...............
Googling says that to fix this all I need to do is add
keep_environment
to exim.conf. What I'm struggling to find out is why it's suddenly needed and what the effects are