Exim and backup relays

[Longman]

* Ian Spray wrote:
> Yup - this is a common problem.  One very quick fix (which works for all 
> systems and not just exim) is a bogus last MX record.  The spammers do 
> tend to start at the lowest numbered MX and work up, so this cuts things 
> down a little, but isn't a full solution:

Highest numbered ?  i.e. Lowest priority.

> The other, exim specific thing is to get your backup MX to test during 
(snip userful comments about exim).

There is also receiver_verify, ignore_errmsg_errors,
ignore_errmsg_errors_after, and timeout_frozen_after to look at.  I use
CHECK_RCPT_VERIFY_SENDER = 'true' but doesn't seem to do much.  Will try
out some of your suggestions, thanks :-)