I have used :fail: in some aliases; when one of these addresses is refused, I see the message on the log, but the response to the remote user is unknown user > instead of the message from the alias file. How can I change this?

Have you got a message qualifier in the relevant ACL? Exim uses the message line in the ACL in preference to the message returned by the router. This is so you can restrict the amount of information that escapes from your site via SMTP if you want to. Remove the message line in the ACL entry that has verify = recipient and your message will get through. Alternatively, if you are running Exim 4.10 or later, you can use the $acl_verify_message variable in your message to include the message from the router. See also `../Q0725`_.

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