Problems with Exim/relay_hosts
The exim.conf line in question is simply:hosts = +relay_hosts
We'll test a host that we know is already in relayhosts:
# cat /etc/relayhosts
69.181.43.251
70.5.115.105
# exim -bh 69.181.43.251
<snip>
>>> sender host name required, to match against lsearch;/etc/relayhosts
>>> looking up host name for 69.181.43.251
>>> IP address lookup yielded c-69-181-43-251.hsd1.ca.comcast.net
<snip>
>>> host in "lsearch;/etc/relayhosts : localhost : 216.22.10.35"? no (end of list)
GRRR! "no"??? What, is it trying to match "c-69-181-43-251.hsd1.ca.comcast.net" rather than the IP address?