It works for me. What version of the Aysnc OS are you running:

ironhost.com> ldapconfig

Current LDAP server configurations:
1. AD_LDAP: (djskd.ironport.com:389)


Choose the operation you want to perform:
- NEW - Create a new server configuration.
- EDIT - Modify a server configuration.
- DELETE - Remove a server configuration.
- SETUP - Configure LDAP options.
[]> edit

Enter the name or number of the server configuration you wish to edit.
[]> 1

Name: AD_LDAP
Hostname: djskd.ironport.com Port 389
Authentication Type: password
Base: dc=domain,dc=com
LDAPACCEPT: AD_LDAP.accept
LDAPGROUP: AD_LDAP.ldapgroup


Choose the operation you want to perform:
- SERVER - Change the server for the query.
- LDAPACCEPT - Configure whether a recipient address should be accepted or bounced/dropped.
- LDAPROUTING - Configure message routing.
- MASQUERADE - Configure domain masquerading.
- LDAPGROUP - Configure whether a sender or recipient is in a specified group.
- SMTPAUTH - Configure SMTP authentication.
[]> lda
ldapaccept, ldaprouting, ldapgroup
[]> ldaprouting

Please create a name for this query:
[AD_LDAP.routing]>

Enter the LDAP query string:
[(mailLocalAddress={a})]> (mail={f})

Please enter the cache TTL in seconds:
[900]>

Please enter the maximum number of cache entries to retain:
[10000]>

Do you want to rewrite the Envelope Recipient? [Y]> n

Do you want to send the messages to an alternate mail host? [Y]>

Enter the attribute which contains the alternate mailhost for the recipients.
[mailHost]>