How to configure exim4 for both incoming SMTP for local delivery and relay for authenticated user

Question

I want to use my exim4 mail server as local delivery for anonymous sender for my localdomains, and relay to everyone only for authenticated users. Is it possible?

Answer 1

My approach is the next:

First we have to define TLS encryption. No auth allowed without TLS.

tls_certificate = /usr/local/etc/exim/exim.crt
tls_privatekey = /usr/local/etc/exim/exim.key
tls_advertise_hosts = *
tls_on_connect_ports = 587 : 465
auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}}

Then we have to define auth mechanism. I prefer to use the same userdb dovecot have used. Keep in mind you need dovecot-auth to be compiled into exim. You can add more auth schemes if you want.

begin authenticators
plain:
 driver = dovecot
 public_name = PLAIN
 server_socket = /var/run/dovecot/auth-client
 server_set_id = $auth1
 server_condition = ${if !eq{$tls_cipher}{}}

login:
 driver = dovecot
 public_name = LOGIN
 server_socket = /var/run/dovecot/auth-client
 server_set_id = $auth2
 server_condition = ${if !eq{$tls_cipher}{}}

Now we can filter out incoming messages

acl_rcpt:
# we accept everything from auth'ed hosts
accept  authenticated   = *

# we accept everything from our trusted hosts/networks
accept  hosts =  : +relay_from_hosts

# all the rest should be addressed to the domains we serve
require domains = +relay_to_domains : +local_domains
. . . . .