<source 0/0> # Matches all other IPs always-allow-relaying no # Reject relaying unless authenticated process-x-virtual-mta yes max-message-size 10485760 smtp-service yes allow-unencrypted-plain-auth no # Reject plain-text passwords over unencrypted channels default-virtual-mta main-pool # Fallback VMTA if none selected </source>

<domain outlook.com> <domain hotmail.com> <domain live.com> <domain msn.com> max-smtp-out 10 max-connect-rate 2/m max-msg-per-connection 50 max-msg-rate 200/h retry-after 5m </domain>

address bounce-handler@example.com reject-non-retryable false max-bounces-per-hour 100

The configuration above watches for specific Microsoft error responses (like 421 RP-001 or 421 4.3.2 System busy ). When detected, PowerMTA automatically shrinks your allowed connection footprint and hourly throughput for a designated cool-down period. Essential Best Practices Beyond the Configuration File

Without SPF, DKIM, and DMARC, a lifestyle brand looks like a counterfeit handbag. Entertainment emails must pass authentication with flying colors.