Best way to tie RT to LDAP?

It appears there’s a variety of ways of tying RT to LDAP.

I have an RT setup going, and now it’s time to add in LDAP somehow.

We have 10’s of thousands of e-mail addresses, and most of them are
under the same domain, but not all of them. The ones that’re off that
magic domain should all already be in an LDAP-accessible database.

What’s the best way of setting up RT to use LDAP in a scenario like
this? Lots of e-mail addresses, but not totally consistent hostnames
in the server part of the addresses.