[Exim] authenticator config problems (newbie)

Hi,

i'm trying to configure exim 4.23 that was preinstalled on my vanilla
rh9 server. i'm using mozilla 1.6 on a remote machine for testing my
e-mail account. currently i can read messages with mozilla, and i can
send messages from server's console using 'mail'. however, when i try
to *send* an e-mail using mozilla and mua tries to connect to smtp
(port 465) server (ie my exim server), it is asked for a password,
which is always rejected. i know the password is correct (i can ssh to
server with it) but exim's log file says the following:
fixed_login authenticator failed for (xxxxxx.com) [68.122.35.1]: 535
Incorrect authentication data (set_id=correctUsername). NOTE, that
set_id is actually one i'm sending.
current authenticator section (i've tried many( of my exim.conf is this:

fixed_plain:
  driver = plaintext
  public_name = PLAIN
  server_prompts = :
  server_condition = \
    ${if and {{eq{$2}{ph10}}{eq{$3}{secret}}}{yes}{no}}
  server_set_id = $2

fixed_login:
driver = plaintext
public_name = LOGIN
server_prompts = "User Name : Password"
server_condition = "\
    ${if pam {$1:$2}{yes}{no}}"
server_set_id = $1

unfortunately, i am new at this, and have little idea what the above
means.

i'd really appreciate if someone could tell me how i can get this to
work. if not, perhaps you could give me some clues:

-how can i see what password exim is receiving from remote client?
-how's that password verified (by checking /etc/shadow?) OR
-is it by using pam (does that mean i have to alter stock
/etc/pam.d/exim and/or add my authentication info to some other file?)
-should i be trying to configure cram_md5 authenticator instead of
plaintext?

thanks a lot

-nikita