SMTPGuard

SMTPGuard is a web app (with optional lightweight agent) that monitors and protects self-hosted and cloud SMTP servers from abuse, misconfiguration, and deliverability-killing events. It continuously checks outbound patterns, queue growth, bounce/complaint signals, authentication posture (SPF/DKIM/DMARC), TLS and cipher health, and common open-relay indicators. When it detects anomalies—like sudden volume spikes, credential stuffing, or new sending domains—it can automatically throttle, block, rotate credentials, or require step-up verification. It also runs scheduled “deliverability preflight” tests to major inbox providers and tracks blacklist status across common lists, with clear remediation playbooks. This is not a full MTA replacement; it’s a pragmatic safety layer for teams that already run Postfix/Exim/Mailcow or use SES/SendGrid but still get burned by compromised accounts, noisy tenants, or subtle config drift. Combination traditional + AI (AI for anomaly detection and guided remediation).