MailWizz Engineering Center · Version 3.8

Bounce Server Engineering

Configure and troubleshoot IMAP/POP3 bounce processing, mailbox sizing, cron cadence, and classification quality.

Engineering approach

1. Document the current topology, versions, ownership, credentials, and traffic flow.
2. Change one controlled variable at a time and preserve before-and-after evidence.
3. Validate from MailWizz, the transport layer, DNS, and the receiving provider—not from one dashboard alone.
4. Monitor queue age, SMTP outcomes, bounce processing, complaints, and database growth after deployment.

Implementation checklist

• Confirm prerequisites and dependencies.
• Use least-privilege service accounts and unique credentials.
• Keep sending identities aligned across visible From, envelope sender, DKIM, PTR, and HELO.
• Prevent overlapping cron executions where duplicate work is unsafe.
• Store logs long enough to investigate delayed provider responses.
• Test rollback and recovery procedures.

Verification

# Record the exact command, timestamp, exit status and relevant log lines.
# Validate one controlled test campaign before restoring normal volume.
# Compare acceptance, delivery, bounce and complaint metrics.

Common mistakes

• Increasing concurrency before finding the actual bottleneck.
• Sharing credentials or sending pools across unrelated customers.
• Ignoring temporary SMTP responses until queues become stale.
• Changing application, relay and DNS settings simultaneously.
• Keeping backups that have never been restored in a test environment.

Related resources

MailWizz Engineering Center · Interactive builders · Deployment examples