Use tools like UltraMailer or a simple terminal test to verify port 587 is open.
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Retrying transient errors intelligently while immediately dropping hard bounces. Comprehensive Sample PowerMTA Configuration File
| Setting | Purpose | |---------|---------| | max-smtp-out / max-msg-rate | Controls sending speed per ISP (Hotmail, Gmail, Yahoo). | | smtp-starttls required | Forces TLS for better deliverability. | | dkim-sign yes | Adds DKIM signature to avoid spam folders. | | bounce-handler / fbl-handler | Handles bounces and abuse complaints automatically. | | dns-servers 8.8.8.8 | Fast, reliable DNS for MX lookups. | | use-rs | Enables recipient verification (RSET before DATA). | sample powermta configuration file hot
| | What It Does | Google (Gmail) Limits | Microsoft (Hotmail/Outlook) | Yahoo | | :--- | :--- | :--- | :--- | :--- | | max-smtp-out | Concurrent connections to a domain | 10 - 20 per IP | 10 - 20 per IP | 10 - 20 per IP | | max-connect-rate | New connections per minute | 2/m per IP | 2/m per IP | 2/m per IP | | max-msg-per-connection | Messages sent per connection | 50 - 100 | 50 - 100 | 50 - 100 | | max-msg-rate | Message per hour to a domain | 200 - 1000/h | 200 - 500/h | 200 - 500/h |
The Ultimate Guide to a High-Volume PowerMTA Configuration File
A high-volume sender must sign emails with DKIM. The directive tells PMTA which key file to use. How to Apply and Test the Configuration Use tools like UltraMailer or a simple terminal
: Tells PowerMTA to attempt redelivery every 15 minutes for temporary deferrals, ensuring fast resolution of temporary graylisting. Best Practices Before Deploying This File
Run pmta reload or pmta check to ensure no syntax errors exist. Restart PMTA: service pmta restart . Best Practices for "Hot" PowerMTA Servers
PowerMTA supports live configuration reloading—a critical feature for production environments: If you share with third parties, their policies apply
Bird (formerly SparkPost) recommends keeping configurations DRY (Don't Repeat Yourself):
This command applies configuration changes without stopping the mailer or dropping existing connections. No restart is required for most directive changes, except: