Email Infrastructure Uptime Monitoring Guide

Email Delivery Failures

Bounced messages, lost transactions, and failed communications with customers or team members

Reputation Damage

Repeated delivery failures can harm your sender reputation with ISPs and email providers

Revenue Loss

Missed transactional emails, order confirmations, and time-sensitive notifications cost money

Customer Trust Erosion

Unreliable email delivery damages customer confidence and satisfaction

SMTP Servers

Monitor your outbound and inbound mail servers for connectivity, response times, and proper SMTP protocol responses. Check that authentication is working correctly.

MX Records

Verify that MX records are resolving correctly and pointing to the right mail servers. Monitor for unexpected changes or DNS propagation issues.

DNS Records

Track availability and content of A records, AAAA records, and PTR records. DNS failures can prevent email delivery even if servers are operational.

Authentication Records

Monitor SPF, DKIM, and DMARC records for availability, correctness, and unexpected modifications. Missing authentication records lead to delivery failures.

TLS/SSL Certificates

Track certificate expiration dates and validate that TLS encryption is functioning properly. Many providers require TLS for email delivery.

Verify SMTP servers accept connections and respond with proper greeting banners. Test authentication mechanisms.

Monitor the standard SMTP port for inbound mail server accessibility and proper message acceptance.

Test the message submission port used by email clients and applications. Verify STARTTLS support.

Monitor the implicit TLS port for secure email submission with built-in encryption.

Check certificate validity, expiration dates, cipher strength, and protocol versions. Alert on weak encryption.

Validate that all DNS records resolve correctly from multiple geographic locations. Monitor query response times.

Continuously verify SPF, DKIM, and DMARC records are present and correctly configured. Alert on changes.

Check Intervals

Choose monitoring frequency based on criticality:

• Critical infrastructure: Every 1-5 minutes (SMTP servers, MX records)
• Important checks: Every 5-15 minutes (DNS resolution, authentication records)
• Standard monitoring: Every 15-30 minutes (TLS certificates, secondary servers)
• Certificate expiration: Daily checks with 30, 14, and 7-day advance warnings

Timeout Settings

Configure appropriate timeouts to balance responsiveness with false positives:

• SMTP connections: 10-30 seconds (servers should respond quickly)
• DNS queries: 5-10 seconds (typically fast, but allow for network latency)
• TLS handshakes: 15-30 seconds (encryption negotiation takes time)

Alert Thresholds

Set thresholds to reduce false alerts while ensuring rapid response:

Email Alerts

Send detailed incident reports to your operations team. Include check results, error messages, and timestamps. Configure separate email addresses for critical vs. non-critical alerts.

SMS Notifications

Use SMS for critical outages that require immediate attention, especially outside business hours. Keep messages concise and actionable.

Webhook Integrations

Connect to Slack, Microsoft Teams, PagerDuty, or other incident management platforms. Automate incident creation and team notifications for streamlined response.

Server Failures

Hardware failures, software crashes, resource exhaustion (CPU, memory, disk space), or service restarts can take mail servers offline.

DNS Issues

Nameserver outages, incorrect record changes, propagation delays, or DNS provider problems prevent mail routing even if servers are operational.

Firewall Changes

Accidental rule modifications, security updates, or network reconfiguration can block SMTP ports and prevent mail server access.

Certificate Expiry

Expired TLS/SSL certificates cause mail servers to reject connections or clients to refuse delivery. Monitor expiration dates proactively.

Network Problems

ISP outages, routing issues, DDoS attacks, or bandwidth saturation can make mail infrastructure unreachable from external networks.

Configuration Errors

Typos in DNS records, incorrect authentication settings, or misconfigured mail server parameters cause delivery failures.

Multiple Check Locations

Monitor from multiple geographic locations to distinguish between local network issues and actual infrastructure problems. This prevents false alerts from temporary regional connectivity issues and ensures you detect problems that only affect specific regions.

Escalation Policies

Define clear escalation procedures based on outage duration and severity:

• 0-5 minutes: Alert on-call engineer via email and Slack
• 5-15 minutes: Escalate to SMS and PagerDuty
• 15+ minutes: Notify team lead and management
• Critical systems: Immediate SMS/phone call for any failure

Status Pages

Maintain a public or internal status page that displays real-time infrastructure health. This reduces support inquiries during incidents and provides transparency to stakeholders. Include current status, incident history, and scheduled maintenance windows.

Maintenance Windows

Schedule regular maintenance windows and suppress alerts during planned downtime. Document maintenance schedules in advance and communicate them to affected teams. Resume monitoring immediately after maintenance completes.

Redundancy and Failover

Monitor both primary and backup mail servers. Configure multiple MX records with different priorities. Verify that failover works correctly by testing backup servers regularly. Set up alerts if failover servers are serving traffic.

Historical Data and Trends

Retain monitoring data for trend analysis. Track uptime percentages, response time patterns, and incident frequency. Use this data to identify degrading infrastructure before complete failures occur and justify infrastructure investments.

1. Alert Receipt and Acknowledgment

Acknowledge the alert immediately to prevent escalation. Review alert details including affected component, check type, error messages, and timestamp. Determine if this is a true positive or false alarm.

2. Initial Diagnosis

Run manual checks to verify the issue. Check server logs, DNS resolution, and network connectivity. Determine scope: Is it a complete outage or degraded service? Which components are affected?

3. Communication

Update status page and notify stakeholders. Provide estimated time to resolution if possible. Post regular updates even if there is no progress to show active investigation.

4. Resolution

Apply fixes based on root cause. Restart services, update configurations, fix DNS records, or replace certificates as needed. Verify resolution with manual tests before relying on automated checks.

5. Verification and Monitoring

Confirm systems return to normal operation. Monitor closely for the next several hours to ensure stability. Send test emails through affected infrastructure to verify end-to-end functionality.

6. Post-Incident Review

Document the incident including timeline, root cause, and resolution steps. Identify preventive measures to avoid recurrence. Update monitoring, alerts, or infrastructure as needed based on lessons learned.