The client side - amavis - doesn't give enough information. Have you had a look at the LDAP server > log? It _could_ be a query size limit, just to add some speculation ;)
Hm in the cases when amavis failed i cant find eny logentries in ldap.log. here are the LDAP limits dn: cn=config changetype: modify replace: olcSizeLimit olcSizeLimit: size.unchecked=1000 - replace: olcSockbufMaxIncoming olcSockbufMaxIncoming: 500000 - replace: olcThreads olcThreads: 25 - replace: olcTimeLimit olcTimeLimit: 120 - replace: olcSockbufMaxIncomingAuth olcSockbufMaxIncomingAuth: 5000000 The server works on a small business 15 - 20 Mails ervery hour. So i dont think the limits seems to small
