Exim seems to be trying to deliver a message every 10 minutes, though the retry rules specify longer times after a while, because it is writing a log entry every time, like this:

1999-08-26 14:51:19 11IVsE-000MuP-00 == example@example.com T=smtp defer
(-34): some host address lookups failed and retry time not reached for
other hosts or connection limit reached

It is looking at the message every 10 minutes, but it isn't actually trying to deliver. It's looking up example.com in the DNS and finding this information:

example.com.                MX 10 example-com.isp.example.com.
example.com.                MX  0 mail.example.com.
mail.example.com.           A  202.77.183.45
A lookup for example-com.isp.example.com. yielded NXDOMAIN

The last line means that there is no address (A) record in the DNS for example-com.isp.example.com. That accounts for some host address lookups failed, but the retry time for mail.example.com hasn't been reached, which accounts for retry time not reached for other hosts.