1. Service availability & SLA targets
MailCheckup monitors core infrastructure availability continuously from multiple independent external monitoring stations. Our service targets and observed metrics are outlined below:
| Subsystem Component | Target SLA | Observed 90-Day Uptime | Performance SLA Target | Fail-Open Safeguard |
|---|---|---|---|---|
| REST Verification API | 99.90% | 99.99% | Sub-180ms p95 latency | 250ms client timeout budget |
| Bulk List Engine | 99.90% | 100.00% | Zero queue backlog | Resumable chunked ingestion |
| Edge SMTP Dialers | 99.90% | 99.95% | RFC 5321 handshake compliance | Distributed regional IP pools |
| Webhook Dispatcher | 99.90% | 100.00% | < 500ms event delivery | Automatic retry with backoff |
| MCP Agent Server | 99.90% | 100.00% | JSON-RPC 2.0 streaming | Bearer auth session isolation |
2. Distributed dialer edge architecture
To deliver consistent sub-180ms verification latency and prevent connection blacklisting, MailCheckup operates distributed SMTP dialing clusters across Tier-1 datacenters in North America and Europe. Nodes maintain strict FCrDNS alignment and dynamic IP warming schedules.
3. Incident management & post-mortem protocol
In the event of an infrastructure anomaly, on-call site reliability engineers are paged immediately. Status updates are published to this dashboard within 15 minutes of detection. Following incident resolution, public post-mortem reports detail root cause analysis and preventative safeguards.
4. Frequently asked status questions
What is MailCheckup's target service availability SLA?
MailCheckup targets 99.9% monthly service uptime across our core single verification API and bulk processing engine. Historical 90-day availability is published live on this dashboard.
How are scheduled maintenance windows communicated?
Routine maintenance is scheduled during low-traffic weekend intervals (typically Sunday 02:00–04:00 UTC). Notifications are posted to this status page and communicated to active API users via dashboard banners 72 hours in advance.
What happens to my API requests during a temporary upstream degradation?
We recommend engineering teams implement our fail-open architectural pattern with a 250ms–350ms AbortSignal budget. If an upstream network timeout occurs, user registration is allowed to proceed and the check is enqueued for free asynchronous re-checking.
Where can I report a suspected service interruption?
If you suspect an outage or abnormal verification latency, email support@mailcheckup.net with your Job ID or API request timestamps for immediate review by on-call site reliability engineers.
Are unknown timeout outcomes billed during upstream provider disruptions?
Never. Under our unconditional $0 Free Unknown Policy, any check that cannot be completed due to network timeouts, firewall blocks, or server deferrals costs 0 credits, and all temporary holds are released.
Does MailCheckup operate multi-region dialer nodes?
Yes. MailCheckup operates distributed SMTP dialing clusters across North America and Europe, optimizing round-trip times and preventing single-datacenter routing bottlenecks.