PowerMTA Troubleshooting
Evidence-first workflows for queues, authentication, DNS, TLS, provider deferrals, security incidents and reporting failures.
Queue growth
Messages enter faster than they leave.
SMTP authentication failures
Submission credentials are rejected.
Unauthorized MAIL FROM
Authenticated users submit unapproved envelope senders.
DKIM failures
Signatures are missing or fail validation.
SPF failures
Envelope sender domain does not authorize the source IP.
DMARC failures
Neither aligned SPF nor aligned DKIM passes.
TLS negotiation failures
Remote TLS negotiation cannot complete.
DNS resolution failures
MX or host resolution fails or is inconsistent.
Wrong VirtualMTA selected
Mail leaves through an unexpected source IP or HELO.
Microsoft S775 or reputation throttling
Microsoft limits traffic due to reputation signals.
Gmail temporary failures
Gmail defers messages.
Yahoo/AOL deferrals
Yahoo or AOL temporarily defers mail.
Hard-bounce spike
Invalid-recipient outcomes rise suddenly.
Complaint spike
User complaints increase.
PowerMTA service does not start
Configuration or environment prevents startup.
Disk or spool pressure
Queue and logs consume available storage.
Unexpectedly low throughput
Delivery is below expected volume.
Duplicate delivery reports
Recipients or systems report duplicates.
Missing accounting records
Expected delivery records are absent.
Compromised SMTP credential
Unexpected mail is submitted with valid authentication.