[exim] Special character in exim.conf

Hi! All:

I'm using LOGIN smtp authentication. When I use client_send to send username and passwd,
I found special characters such as $ and ^ will cause authentication fail.
I've tried to use backslash to escape special character, but it seems not worked.
What are the all special characters recognized by exim.conf? How can I escape them?
Thanks in advance.

Best,
Latrell