Configuring PowerMTA (PMTA) effectively requires moving beyond a simple "install and send" mentality to a structured environment optimized for deliverability and scalability 1. Environment Prerequisites
Before touching the configuration file, ensure your infrastructure is ready: Server Specs
: A VPS or dedicated server with at least 2GB of RAM (8GB recommended for high volume). Operating System : Current guides recommend Ubuntu 20.04+ or CentOS 8+. powermta configuration guide top
: A fixed IP address is critical for building a stable sender reputation. Port Access
: Port 25 must be open for server-to-server relay, and port 587 is recommended for secure email submission. 2. Core Configuration ( /etc/pmta/config Smart throttling with feedback loop: <domain gmail
The main configuration file dictates how PMTA behaves globally and for specific domains. Authentication & Basics : Define your license and basic server identity.
license-key "YOUR_LICENSE_KEY" host-name mail.yourdomain.com smtp-listener 0/0:25 Use code with caution. Copied to clipboard Source Directives Smart throttling with feedback loop: <
: 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
<domain gmail.com>
<limits>
throttle 1000/hour
error-throttle 500/hour on 4xx,5xx
defer-throttle 200/hour on 421,450
</limits>
</domain>
error-throttle reduces sending when ISP rejects (hard bounce), defer-throttle cuts rate on soft errors.
Security is paramount. An open relay will get your server blacklisted immediately.
Allocate huge pages for queues:
queue-mem-pool-size 2048M
large-message-threshold 262144 # 256KB