Email Service Level Agreements: What Your SLA Should Actually Cover
What an Email SLA Actually Promises
An email service level agreement spells out exactly what a hosting or infrastructure provider commits to delivering — uptime, support response time, delivery guarantees, and what compensation you're owed if they fall short. For most businesses, email is infrastructure they can't afford to lose. Understanding what your email SLA covers — and what it quietly doesn't — is the difference between a supplier you can hold accountable and one that shrugs when something goes wrong.
The headline number on most email SLAs is uptime: 99.9%, 99.95%, 99.99%. These percentages look similar but translate to very different amounts of allowable downtime per year:
- 99.9% uptime = up to 8.7 hours of downtime per year
- 99.95% uptime = up to 4.4 hours of downtime per year
- 99.99% uptime = up to 52 minutes of downtime per year
For a business that receives time-sensitive customer inquiries, contract negotiations, or order confirmations by email, the gap between those numbers has a real dollar value. Know precisely what you're buying.
What Should Be in an Email SLA
A Clear Definition of "Uptime"
Read carefully how uptime is defined. Some providers define it as the percentage of time the service responds to a health check ping — which is a very different measurement from email actually being deliverable. A server that's "up" but dropping inbound SMTP connections isn't up in any sense that matters to your business. The SLA should specifically cover SMTP acceptance, IMAP and POP3 availability, and webmail access as separate measured components, each with its own commitment.
Scheduled Maintenance Windows
Most SLAs carve out scheduled maintenance from uptime calculations. A provider that schedules 4 hours of maintenance per month without counting it toward downtime can still claim 99.9% uptime while your email is unavailable for hours each month. Check whether maintenance windows are pre-announced, how much advance notice is given, and whether they're limited to low-traffic hours in your timezone.
Support Response Time Commitments
Uptime SLAs tell you how long the service can be down. Support SLAs tell you how quickly someone responds when it is. The distinction matters: a 20-minute outage with no acknowledgment for 4 hours is worse operationally than a 2-hour outage with immediate communication and a clear timeline. Look for tiered commitments:
- Critical issues (service completely unavailable): 15–30 minute initial response
- Major issues (degraded service affecting users): 1–4 hour response
- Minor issues (non-urgent questions): 24-hour response
SLA Credits and How to Claim Them
Credits are the compensation a provider offers when they fall below their commitments. Common structures offer service credits as a percentage of your monthly fee based on how far below the SLA threshold actual uptime fell. A typical structure:
- 99.0–99.9% actual uptime: 10% monthly credit
- 95.0–99.0% actual uptime: 25% monthly credit
- Below 95%: 50% monthly credit
Read the claim process. Credits that require you to submit a ticket within 48 hours of an incident, attach server logs, and wait 30 days for processing are less useful than automatic credits applied based on provider-side monitoring. Some providers make credits nearly impossible to collect in practice even when they're theoretically available — know which kind you're dealing with before a problem occurs.
Data Backup Commitments
Does the SLA specify how frequently your email data is backed up, where those backups are stored, and how quickly data can be restored following an incident? A provider who guarantees uptime but makes no commitment on backup frequency or recovery time leaves you exposed if server-side data is corrupted or lost during an outage. Backup frequency and recovery time objectives (RTO) should be explicitly stated.
Security Incident Notification
If a security breach affects your email data, how quickly will the provider notify you? GDPR requires notification within 72 hours of discovery. A compliant provider will have this in their SLA — along with a commitment about what information will be shared: the nature of the breach, data affected, remediation steps taken, and what you should do next.
Questions to Ask Before Signing
Before accepting any email service agreement, get clear answers on:
- How is uptime measured and by whom — provider-side only, or verified by an independent monitoring service?
- What categories of events are excluded from the SLA calculation?
- How do I claim a credit, and what's the processing timeline?
- Where is my data stored, and in how many physical locations?
- What happens to my data if I want to leave the service?
- How quickly can service be restored from backup following a major incident?
Reading Between the Lines
The SLA is a floor, not a description of normal operations. A reputable email provider should be operating well above their SLA commitment on a day-to-day basis. The SLA exists to govern what happens when things go wrong. Ask prospective providers for their actual historical uptime data — providers who are confident in their infrastructure will share it readily.
MailDog's email hosting is built on redundant infrastructure designed for business reliability. Review the service tiers and frequently asked questions, or get in touch to discuss specific uptime and support requirements for your organization. For context on how operational discipline maps to infrastructure reliability, see our overview of email operations KPIs.
