Throttling protects you from being blacklisted. Configure per-domain policies:

<domain gmail.com> max-msg-per-hour 200000 # Respect Gmail's limits max-msg-rate 50/second # Slower warmup dns-timeout 45 use-starttls yes # Always TLS if available </domain>

Securing your server against open relay exploitation is critical. If unauthorized users hijack your PowerMTA server to send spam, your IPs will be blacklisted globally within minutes. Restricting Access via ACLs (Access Control Lists)

This guide breaks down the you need to master. We will move from basic syntax to advanced performance tuning.

smtp-source-ip 192.0.2.10 host-name ://yourdomain.com smtp-source-ip 192.0.2.11 host-name ://yourdomain.com Use code with caution. Creating MTA Pools

The PowerMTA configuration file is usually located at /etc/powermta/config or /etc/powermta/powermta.conf . The configuration file consists of several sections, including:

logrotate /var/log/powermta.log daily missingok notifempty delaycompress compress maxsize 100M maxage 7 postrotate /usr/sbin/powermta reload endscript

Attach to VMTA:

: Use these to manage headers and control which sources can relay through your server. DKIM Signing : Implement 2048-bit DKIM keys for authentication. Rate Limiting max-smtp-out max-msg-per-connection to avoid overwhelming ISPs. For example, setting max-msg-per-connection 100 aligns with most ISP acceptance rates. 3. Advanced Deliverability Features Which SMTP Port to Use? Understanding ports 25, 465, & 587

The main configuration file is located at /etc/pmta/config . This file controls how PowerMTA initializes resources, binds to network interfaces, and logs data. Defining Global Constants

By maintaining structured configurations, grouping your traffic intelligently via VirtualMTAs, and respecting ISP-specific limits, your PowerMTA infrastructure will easily sustain high deliverability rates at enterprise scale.