[exim] ACL question

Hello Guys,

I am scratching my heads over 3 days and couldnt find answer yet. So, you
guys are my last hope now. We are running exim , IMAP and mysql on one
box. I must have to accept

local_domains and local_hosts in ACL. But still anyone can send email to my
domain users via telnet 25 other than relay. How can I solve this issue.

My configuration is as

acl_check_rcpt:

accept hosts = :

 accept  domains       = +local_domains
           endpass
           message       = unknown user
           verify        = recipient
accept  hosts         = +relay_from_hosts

accept authenticated = *

 deny    message       = relay not permitted

For example my virtual domain is abc.com

From outside:

telnet mymailserver 25

helo test
mail from:test@???
250 OK
rcpt to:test@???
250 Accepted
data
354 Enter message, ending with "." on a line by itself
hello
.
250 OK id=1K51XZ-00084q-SF

so, I can write script that can generate fair enough spams. How can we
overcome on this? Any help would be appreciated.

Thanks,

Farhan