[exim] VRFY and LDAP defers

We're setting up some Proofpoint demo boxes and using SMTP VRFY
callouts to our exim (4.20) relays to verify recipients. It appears
that when the LDAP server returns a DEFER, that the entire LDAP error
(including search string, bind dn and passwd) are passed back to the
Proofpoint box and nothing is logged by exim.

I can't exactly verify this yet, as the DEFERs are rather few and far
between and I can't go change the exim config without jumping through
bureaucratic hoops. We're going to narrow it down to one exim relay
(instead of 3 behind a load balancer) and then compare it to a 4.60
test box, but I thought I'd see if folks might have seen this before.

K.