Você pode usar o seguinte acl
acl_smtp_rcpt = acl_check_rcpt
acl_check_rcpt:
deny
message = The $sender_address is prohibited to send mail to the $domain
senders = lsearch;/etc/exim/restricted_sender
domains = lsearch;/etc/exim/restricted_domains
/etc/exim/restricted_sender
[email protected]
/etc/exim/restricted_domains
gmail.com
Teste
# swaks -s mail.example.net --to [email protected] --from [email protected]
=== Trying mail.example.net:25...
=== Connected to mail.example.net.
<- 220 mail.example.net, [xxx.xxx.114.28]
-> EHLO www.example.net
<- 250-mail.example.net Hello www.example.net [xxx.xxx.114.28]
<- 250-SIZE 52428800
<- 250-PIPELINING
<- 250-STARTTLS
<- 250 HELP
-> MAIL FROM:<[email protected]>
<- 250 OK
-> RCPT TO:<[email protected]>
<** 550 The [email protected] is prohobited to sent mail to the gmail.com
-> QUIT
<- 221 mail.example.net closing connection
=== Connection closed with remote host.