I'm trying this out. Things aren't working so well.
The exim FAQ suggests this hack:
login:
driver = plaintext
public_name = LOGIN
server_prompts = Username:: : Password::
server_condition = \
${if eq {${readsocket{/var/run/courier/authdaemon/socket}\
{AUTH 76\n${length_76:exim\nlogin\n$1\n$2\
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n}}}}{FAIL\n} {no}{yes}}
server_set_id = $1
That didn't work out of the box. Surprise.
I realized that courier 3.0.2 changed things to:
/var/run/authdaemon.courier-imap/socket
So I tried that change too.
No Luck.
Anyone have this going?