This is an old revision of the document!
useful commands and hints..
generate, check and activate aliases:
makealiases; makealiases -chk; courier flush
mailq displays a list of all messages that have not been delivered yet:
mailq|less
find relay errors:
grep "error,relay" /var/log/mail.log|less
courieresmtpd: error,relay=::ffff:9x.2×6.7x.1×5,from=mail@domain.net,to=mail@domain.net: 513 Relaying denied.
make sure the client has outbound authentication checked within their email client.
(This is the second method if pop-before-smtp fails.)