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.
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Connect to the server via SSH
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Enable rejection of DMARC failed messages
# plesk bin settings -s mail_dmarc_reject_at_smtp=true && plesk repair mail -y