Symptoms
Delivery reports, like bounced email notifications, fail to send when emailing a non-existent email address, with these errors in /var/log/maillog
[email protected], relay=none, delay=0.19, delays=0.19/0/0.01/0, dsn=5.4.4, status=bounced (Host or domain name not found. Name service error for name=example.com type=AAAA: Host not found)
DKIM Feed: No signature
DMARC: smtpdomain= maildomain=plesk.example.com [email protected] stamp=1701353376 ip=unknown adkim=relaxed aspf=relaxed p=REJECT sp=UNSPECIFIED pct=100 align_dkim=fail align_spf=fail spfres=unknown dkimres=unknown dmarccheck=DMARC_POLICY_REJECT dmarcstatus=STOP
postfix-local[29983]: message discarded by a mail handler
Cause
DMARC checks are enabled, and the bounce back email is sent from a MAILER-DAEMON that is not associated with a domain, so DMARC fails. When DMARC checks fail, the email is discarded, so no bounce back message is generated.
Resolution
Configure the mail server to reject emails that fail the DMARC check.
Connect to the server via SSH
Enable rejection of DMARC failed messages
# plesk bin settings -s mail_dmarc_reject_at_smtp=true && plesk repair mail -y
