[exim] POP/IMAP and Exim (4.43)

Hi,

it probably seems like a very obvious answer to my questions, but I'm just
not experienced enough to know how these servers tie-in and work together...

I have Courier and Exim installed and things seem to work ok, but I
apparently do not have AUTHentication setup/configured, at least not with
Exim. I've compiled Exim myself and included AUTH_CRAM_MD5=yes
AUTH_PLAINTEXT=yes AUTH_SPA=yes, but when I 'telnet localhost 25' I do not
get '250-AUTH PLAIN LOGIN CRAM-MD5'.

And now to my questions - do I have to configure AUTHentication in Exim, in
Courier, or both? Do I even need POP/IMAP servers with Exim, and if not,
what would be a situation where I'd want POP/IMAP servers running?

As I see it, POP/IMAP servers are there to act as the front-end to the MTA
for MUAs, which is why I'm wondering if I even need to configure
AUTHentication in Exim, but I'm just not sure.

Thanks for your help!
Robert