[exim] Login authenticator takes very long time

I have an exim install handling a lot of users and domains. 99.9999% of
the users use webmail, so I have never had an issue. However, I have
recently had a few users request the use of an outside client
(Thunderbird), so I am setting up an authenticator. Here is what I have:

begin authenticators

login:
driver = plaintext
public_name = LOGIN
server_prompts = "Username:: : Password::"
server_condition = "${if crypteq{$2}{${extract{1}{:}{${lookup{$1}lsearch{/etc/exim/config/auth.users}{$value}{*:*}}}}}{1}{0}}"
server_set_id = $1

This works, and works great. However, it takes FOREVER to happen. I
setup Thunderbird to use authentication and when I send a message, it
takes sometimes more then 30 seconds to ask for the password. Once I
enter the password, the message is sent immediately. I have tried
disabling the hostname lookups, and nothing changes.

Any suggestions?
--
Matthew Daubenspeck

Gentoo Linux i686 Intel(R) Xeon(R) CPU L5420 @ 2.50GHz
21:57:04 up 46 days, 5:15, 8 users, load average: 0.04, 0.07, 0.02