Using LDAP for email aliases

As I gradually migrate various servers to using LDAP as the auth back end, it occured to me that there was some duplication going on in terms of adding the users' email addresses to the LDAP so that they could be looked up on clients and then having an aliases file that was being used by exim to do the delivery.

So I've come up with the following for allowing exim to take advantage of the email addresses stored in the LDAP database:

### router/450_local_ldap_aliases
#################################

# This router handles aliasing looking up email addresses in an ldap database.
#

ldap_aliases:
debug_print = "R: ldap_aliases for $local_part@$domain"
driver = redirect
domains = +local_domains
allow_fail
allow_defer
data = ${lookup ldap {ldap://127.0.0.1/ou=Users,dc=...?uid?sub?(mail=$local_part@$domain)}}