MailWizz Cold Start — Complete Infrastructure Setup and Warming Guide for New Deployments

Starting a new MailWizz deployment with new sending infrastructure requires a structured sequence: infrastructure setup, authentication verification, and gradual warming before any production volume. This guide covers the complete sequence from server provisioning to first production send.

Pre-Launch Infrastructure Checklist

• DNS: A records, MX records (if receiving bounces), PTR records for all sending IPs
• SPF: TXT record published for each sending domain listing all sending IPs
• DKIM: Keys generated, configured in PowerMTA, selector TXT records published in DNS
• DMARC: Policy published (p=none minimum) with rua reporting address
• Tracking domain: SSL certificate installed, DNS pointing to MailWizz server
• Bounce mailbox: IMAP accessible, php-imap extension confirmed loaded
• Cron jobs: All required cron entries configured and tested as the web server user
• Delivery Server: MailWizz connected to PowerMTA, test email sent and confirmed

Authentication Verification Before First Send

# Send a test message to yourself
# View raw headers in Gmail (View Original)

# Must see:
# Authentication-Results: mx.google.com;
#   dkim=pass header.i=@yourdomain.com
#   spf=pass
#   dmarc=pass

# If any authentication fails, stop and fix before sending to subscribers

First Campaign Requirements

• List must contain only confirmed opt-in subscribers from recent activity (within 6 months)
• Start with highest-engagement segment (opened email in last 30 days preferred)
• Maximum 2,000 subscribers for first send — regardless of list size
• Monitor Google Postmaster Tools integration for Gmail domain reputation immediately after first send
• Check PowerMTA accounting log for unusual deferral patterns within first hour

Week-by-Week Warming Targets

Week 1:  2,000 messages/day  → Monitor: <3% deferral rate
Week 2: 10,000 messages/day  → Monitor: Postmaster spam rate <0.08%
Week 3: 50,000 messages/day  → Monitor: Microsoft SNDS complaint rate GREEN
Week 4-5: 200,000/day       → Monitor: All signals stable
Week 6+: Full volume         → Continue daily monitoring

Troubleshooting Common Issues

Production MailWizz deployments encounter predictable issues at predictable stages. Understanding the diagnostic workflow for the most common problems in this configuration area saves time and prevents the escalating complexity that comes from applying fixes to a misdiagnosed problem. The diagnostic approach is always the same: identify the symptom precisely (not just "it's not working"), isolate the layer where the failure occurs (MailWizz application, delivery server connection, DNS, ISP rejection), and fix at the correct layer.

Systematic Diagnosis Approach

Check MailWizz logs first (available in Backend → Misc → Application Logs), then check the delivery server SMTP logs, then check the PowerMTA accounting log. Most issues surface in one of these three places. A problem that does not appear in any of these logs is almost always a configuration issue — the system is not attempting what you expect it to attempt.

# MailWizz diagnostic log locations:
# Application logs: Backend → Misc → Application Logs
# Delivery logs: Backend → Campaigns → [Campaign] → Delivery Logs
# Bounce logs: Backend → Bounce Servers → [Server] → Logs

# Server-side logs:
# MailWizz application: /path/to/mailwizz/apps/common/runtime/application.log
# PowerMTA delivery: /var/log/pmta/pmta.log
# PowerMTA accounting: /var/log/pmta/accounting.csv

Performance Optimization for Production Scale

MailWizz performance at scale depends on three infrastructure layers: the web application server (PHP/nginx or Apache), the database (MySQL — query optimization is critical at high subscriber counts), and the delivery infrastructure (PowerMTA connection pool sizing). Performance problems in any of these layers manifest as slow campaign sends, delayed processing, or timeouts that appear unrelated to the specific configuration area being managed.

The most common performance constraint in production MailWizz environments is MySQL query efficiency. As subscriber lists grow beyond 500,000 records, unoptimized database queries for segmentation, bounce processing configuration, and campaign statistics become significant bottlenecks. Ensure that subscriber tables have appropriate indexes on email, status, date_added, and any custom field columns used for segmentation.

# MySQL optimization for large MailWizz installations
# Check slow query log:
SHOW VARIABLES LIKE 'slow_query_log%';
SET GLOBAL slow_query_log = 'ON';
SET GLOBAL long_query_time = 1;  # Log queries over 1 second

# Key indexes to verify exist:
SHOW INDEX FROM mailwizz_lists_subscribers;
# Should have indexes on: email, status, date_added, list_id

# Add missing index if needed:
ALTER TABLE mailwizz_lists_subscribers 
  ADD INDEX idx_email_status (email, status);
  
# Campaign sends table — index on campaign_id + subscriber_id:
ALTER TABLE mailwizz_campaigns_tracking_opens
  ADD INDEX idx_campaign_sub (campaign_id, subscriber_id);

Security Considerations

MailWizz installations handling production sending volumes are valuable targets. Key security practices: use HTTPS for all MailWizz access (including tracking and unsubscribe links), restrict Backend access to authorized IP ranges via web server configuration, rotate API keys periodically and revoke unused keys, maintain regular database backups (automated, offsite), and ensure PHP and MailWizz are kept current with security patches.

The tracking domain (used for open and click tracking) requires special attention: it must have a valid SSL certificate (Let's Encrypt is acceptable), and its DNS records must point exclusively to your MailWizz server. A compromised tracking domain can redirect recipients to malicious sites or reveal subscriber click data to third parties.

Campaign Analytics Integration

Track this MailWizz configuration area through two complementary metric layers: MailWizz campaign statistics (open rate, click rate, bounce rate, unsubscribe rate) and PowerMTA accounting log data (ISP-specific deferral rate, bounce classification, queue depth). Gaps between the two layers reveal delivery problems invisible to MailWizz statistics alone — high MailWizz "sent" counts with elevated PowerMTA deferral rates indicate a queue buildup that campaign dashboards don't surface.

Review campaign metrics against your own historical baselines rather than industry benchmarks. Your list composition, acquisition source, and engagement history define what normal looks like for your environment. Use rolling 7-day and 30-day averages to distinguish trend changes from campaign-specific variance.

Implementation Checklist

Before deploying this configuration to production MailWizz, verify: delivery server connection test passes in Backend → Servers → Delivery Servers, cron jobs are running on the correct schedule, bounce server mailbox is accessible and IMAP credentials are valid, tracking domain has valid SSL and loads within 500ms, and PHP memory limit is set to at least 256MB.

After deploying, send a test campaign to a controlled list of seed addresses across Gmail, Outlook, and Yahoo. Verify Authentication-Results headers show dkim=pass and spf=pass in the received messages. Check that open and click tracking are registering correctly in MailWizz statistics. Confirm bounce processing is updating subscriber status within 15 minutes of a test bounce event.

For managed MailWizz environments operated by Cloud Server for Email, these verification steps are performed automatically after any configuration change. The managed service includes continuous monitoring of delivery server health, cron job execution, and tracking domain availability. Contact infrastructure@cloudserverforemail.com for information about managed MailWizz hosting.

Complete Warming Plan with MailWizz

Create engagement segments before starting: Score 5 (opened last 30 days), Score 4 (30-60 days), Score 3 (60-90 days), Score 2 (90-180 days), Score 1 (never opened). Week 1-3: Score 5 only. Week 4: add Score 4. Week 5-6: add Score 3. Each week, expand to the next engagement tier only when deferral rate at major ISPs remains below 5%.

Warming Failure Signals in MailWizz

Warming is failing when: open rate is below 10% on Score 5 segment (indicates list quality problem), bounce rate above 2% on any segment (indicates acquired addresses are invalid), or PowerMTA deferral rate above 10% at Gmail (indicates ISP is restricting new IP). Stop at current warming phase, investigate the specific failure, address it before continuing the ramp.