FAQ / General Debugging / Q0005
Q0005
Question
Why is Exim not rejecting incoming messages addressed to non-existent users at SMTP time?
Answer
This is controlled by the ACL that is run for each incoming RCPT command. It is defined by the acl_smtp_rcpt option. You can check this part of your configuration by using the -bh option to run a simulated SMTP session, during which Exim will tell you what things it is checking.
FAQ / General Debugging / Q0005