error slapd <= bdb_substring_candidates: (mail) not indexed

I have a problem about dig core-8.4.0-783_148.1 when I send a mail I receive this error log:
“Slapd [710]: <= bdb_substring_candidates: (mail) not indexed”.
The error occurs only when sending to external addresses, but saving the address in the address book the sending of the mail works without receiving the error.

Hi @f.pigliacelli ,

If you add the mail attribute to your LDAP indices the error should go away. You can find articles about updating indices in our knowledge base and administrator manual.

@fbartels said in error slapd <= bdb_substring_candidates: (mail) not indexed:

If you add the mail attribute to your LDAP indices the error should go away. You can find articles about updating indices in our knowledge base and administrator manual.

I followed the guide here is what I see:
root@serverk:~# slapcat -b cn=config | grep olcDbIndex:
5939b3af ldif_read_file: checksum error on "/etc/ldap/slapd.d/cn=config.ldif"
5939b3af ldif_read_file: checksum error on "/etc/ldap/slapd.d/cn=config.ldif"
olcDbIndex: objectClass eq
olcDbIndex: cn eq,sub
olcDbIndex: gidNumber eq
olcDbIndex: mail eq
olcDbIndex: memberUid eq
olcDbIndex: ou eq
olcDbIndex: uid eq
olcDbIndex: uidNumber eq
olcDbIndex: uniqueMember eq
olcDbIndex: kopanoAccount eq,pres
olcDbIndex: kopanoAliases eq
olcDbIndex: kopanoViewPrivilege eq
olcDbIndex: sn eq,sub
olcDbIndex: givenName eq,sub

When I send mail from webapp, receive the message:
“Impossible to solve user”.
When I send mails to local users or saved in my phonebook i do not get any errors and the sending works.

I found this:
https://jira.kopano.io/browse/KC-709

@f.pigliacelli yes, that is currently a known issue and being investigated.

after update to kopano core-8.4.0-792_149.1-Debian_8.0-amd64, send mails to local and external users from webapp, but the log “<= bdb_substring_candidates: (mail) not indexed” persists.