<= mdb_substring_candidates: (mail) not indexed

[cbnidk]

I have this in syslog when sending mail from webapp to local users

slapd[1632]: <= mdb_substring_candidates: (mail) not indexed

but I have index mail, how can I fix this
I have ubuntu 18.04 and kopano core 10.0.3 from 9-4-2020
webapp 4.0.2705+1587.1
everything else is working

root@kopano:/# slapcat -b cn=config | grep olcDbIndex:
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
olcDbIndex: objectClass eq
root@kopano:/# cat /var/log/syslog |grep mdb_substring_candidates
May 8 07:05:18 kopano slapd[11673]: <= mdb_substring_candidates: (mail) not indexed
May 8 07:05:18 kopano slapd[11673]: <= mdb_substring_candidates: (mail) not indexed

Claus

[jengelh]

The obvious shot in the dark: olcDbIndex: mail eq,sub

[cbnidk]

Yes now the log is gone, it was
olcDbIndex: mail eq,sub

Claus