[exim] Control mail sending to specific domains

Hi

I'm new to Exim.

Can any one please let me know how to restrict Exim to send mails only to specified domains.

I've done the following setting in exim.conf



domainlist relay_to_domains = mydomain.com



But when a mail is sent to a different domain other than mydomain.com, it seems to go thru. I've configured Exim to transfer all mails to an external mail provider using an SMTP account as follows -



begin routers

smarthost:

driver = manualroute

domains = ! +local_domains

transport = remote_smtp

route_list = * external.mail.server



begin authenticators

fixed_login:

driver = plaintext

public_name = LOGIN

client_send = : myaccount@??? : Password



exim_main.log shows

2009-11-30 10:15:07 KTWNV4-0001L8-Q0 => other.user@??? R=smarthost T=remote_smtp H=external.mail.server [123.4.5.6] X=TLSv1:RC4-MD5:128

2009-11-30 10:15:07 KTWNV4-0001L8-Q0 Completed