Is there a way to exim4 -bP @? exim4 -bt local_user@$(hostname -f | cut -f 1-4 -d '.') succeeds only when I explicitly add $(hostname -f | cut -f 1-4 -d '.') to /etc/exim4/update-exim4.conf.conf:dc_other_hostnames. exim4 -bP +local_domains does have @ as its first component.