Although Mutt can query LDAP directories for addresses directly, sometimes connectivity to LDAP server is troublesome (firewalls, company policies, etc). One way to go around this problem would be to create Mutt addressbook regularly from the content of LDAP directory. This script does exactly this. Specify which LDAP server to query, the branch where people records are, and the filter to use. Output can be redirected to the file of your choice.