[Exim] Address Verification - Sender/Callout

Greetings,

Exim 4.12

Recently I made some changes to my exim.conf file to add RBL and some other
security/spam improvements as suggested by users on the list. I'm happy to
say that by doing so I've cut the amount of spam entering my system by at
least half. One change that was suggested that I have yet to try, is the
use of the sender/callout (callback) feature in the ACL section of the
config file.

I've been reading up on the feature in the documentation, and I'm wanting
to configure the directive so the callout has a "timeout" of maybe 15
seconds (from the 30 sec default). The documentation states the following
for this kind of setup:

verify = sender/callout=5s

But like the documentation notes, I also want to configure the feature to
suppress the details that get returned to the connecting host/SMTP as much
as possible (I don't want the system giving out unnecessary info). The
documentation say this is accomplished via the "no_details" switch:

verify = sender/no_details

Is it possible to combine these two so that the timeout is set to 10-15
seconds -and- to have few details provided to the connecting host via the
"no_details" directive? If that's possible, what would be the correct
syntax? Would it simply be:

verify = sender/callout=15s/no_details

I don't (yet) fully understand the use of these along with the
"callout_defer_ok" and "defer_ok" switches..<?>

Thanks in advance for any tips or suggestions.

Best Regards
Craig