Demystify email failures with human-readable SMTP diagnostics
Never wonder why an email wasn't delivered. Mailofly decodes cryptic raw SMTP error strings into actionable categories: mailbox full, invalid domain, rate-limited, or blocked content.
SMTP reply codes parsed
Soft vs. hard classification
Automatic list suppression
Engineered for developer velocity
Human-readable explanations
Translates '550 5.1.1 User unknown' into clear guidance on why the delivery failed and what steps to take.
Smart suppression list
Hard bounces and spam complaints are automatically suppressed to protect your domain reputation from repeated re-sends.
Searchable failure logs
Filter by recipient, timestamp, status code, or error reason in seconds.
How it works
Inspect bounced message
Click into any failed send in your mail logs to view the full raw and parsed SMTP response.
Review remediation tips
Follow clear instructions to fix DNS issues, unblock addresses, or notify users.
Manage suppression rules
Temporarily whitelist or permanently suppress addresses with one click.
Explore related features
Automated webhook events
Receive instant HTTPS event webhooks for every message state change with cryptographic HMAC signature verification and automatic retries.
Real-time deliverability radar
Continuous deliverability telemetry across Gmail, Yahoo, Microsoft 365, and corporate ISPs with early throttling warnings.
Auditability & event verification
Immutable message history and cryptographic proofs that confirm exactly when an email was dispatched, accepted, and opened.
Ready to build with Instant bounce diagnostics?
Join thousands of engineering teams delivering transactional and lifecycle email with blazing speed and zero downtime.