[exim] DEFER: ldap search initiation failed

I've built up a couple of exim boxes to replace some sendmail
mailrouters. I've got it setup to mimick the sendmail servers while I
work on the transition.

I had them running in the group and everything seemed to be working
fine, except about 3 times a minute, I would get an error message
"DEFER:ldap search initiation failed".

I've checked the addresses that failed, and they are just random
addresses. Some exist, some don't etc etc. We've checked the ldap
server to see if it saw any problems, and it saw no attempt to even
connect.

I ran the server with a -d-all+lookup and got a session that failed.

--------------------------------------------------------------------------
2045 Process 2045 is handling incoming connection from [1.2.3.4]
2045 Process 2045 is ready for new message
2045 search_open: lsearch "/etc/exim/local-routed"
2045 search_find: file="/etc/exim/local-routed"
2045 key="stderr.efficientimpacte.com" partial=-1 affix=NULL
starflags=0
2045 LRU list:
2045 :/etc/exim/local-routed
2045 End
2045 internal_search_find: file="/etc/exim/local-routed"
2045 type=lsearch key="stderr.efficientimpacte.com"
2045 file lookup required for stderr.efficientimpacte.com
2045 in /etc/exim/local-routed
2045 lookup failed
2045 search_open: ldapm "NULL"
2045 search_find: file="NULL"
2045 key="user="uid=something" pass="else"
ldap:///o=top?mailRoutingAddress,mailHost,objectClass?sub?(&(mailLocalAddress=3-1546081-domain.net?wendling@???)(objectClass=inetLocalMailRecipient))" partial=-1 affix=NULL starflags=0
2045 LRU list:
2045 :/etc/exim/local-routed
2045 End
2045 internal_search_find: file="NULL"
2045 type=ldapm key="user="something" pass="else"
ldap:///o=top?mailRoutingAddress,mailHost,objectClass?sub?(&(mailLocalAddress=3-1546081-domain.net?wendling@???)(objectClass=inetLocalMailRecipient))"
2045 database lookup required for user="something" pass="else"
ldap:///o=top?mailRoutingAddress,mailHost,objectClass?sub?(&(mailLocalAddress=3-1546081-domain.net?wendling@???)(objectClass=inetLocalMailRecipient))
2045 LDAP parameters: user=something pass=else size=0 time=0 connect=-1
dereference=0
2045 perform_ldap_search: ldapm URL =
"ldap:///o=top?mailRoutingAddress,mailHost,objectClass?sub?(&(mailLocalAddress=3-1546081-domain.net?wendling@???)(objectClass=inetLocalMailRecipient))" server=ldap2.backbone port=0 sizelimit=0 timelimit=0 tcplimit=-1
2045 after ldap_url_parse: host=ldap2.backbone port=0
2045 ldap_initialize with URL ldap://ldap2:389/
2045 initialized for LDAP (v3) server ldap2:389
2045 LDAP_OPT_X_TLS_TRY set
2045 binding with user=something password=else
2045 Start search
2045 ldap search initiation failed
2045 lookup deferred: ldap search initiation failed
2045 LOG: MAIN REJECT
2045 LOG: MAIN REJECT
2045 H=brightmail1.otherdomain.net (brightmail1.otherdomain.com)
[69.63.44.2]
F=<3-1546081-domain.net?wendling@???>
temporarily rejected RCPT <wendling@???>: ldap search initiation
failed
2045 LOG: smtp_connection MAIN
2045 SMTP connection from brightmail1.otherdomain.net
(brightmail1.otherdomain.com) [1.2.3.4] closed by QUIT
2045 search_tidyup called
2045 unbind LDAP connection to ldap2.backbone:389
1755 child 2045 ended: status=0x0
------------------------------------------------------------------------------

I'm not sure where to go with troubleshooting this further. Does anyone
have any suggestions?