Unique inboxes
Per virtual user
Provision fresh inboxes per test run or per virtual user to keep flows isolated.
Add real inboxes to load tests and stress runs
MailSlurp lets teams provision unique inboxes during load tests and validate that email-dependent flows like signup, password reset, magic links, and notifications keep working under pressure. Use it with K6, JMeter, Locust, or your own harness.
Deterministic waits
Match and assert
Wait for matching emails and assert on subjects, senders, and content signals.
Framework friendly
K6, JMeter, Locust
Use standard HTTP calls to create inboxes and verify messages inside any load test stack.
Operational insight
Measure reliability
Track missing emails and latency under load and turn failures into actionable defects.
Core capabilities
What teams need when email workflows matter
Provision inbox cohorts at scale via API
Create disposable inboxes quickly so load tests can simulate real user flows that depend on email.
- Inboxes
- REST API
- Automation
Wait for matching emails and validate outcomes
Use deterministic wait patterns to capture messages and assert on the signals that matter.
- Wait APIs
- Subjects
- Matchers
Measure failures and latency under load
Detect missing emails, timeouts, and slow delivery patterns so teams can fix bottlenecks before incidents.
- Latency
- Missing messages
- Reliability
Catch defects like broken links and missing images
Pair load tests with audits that detect content defects that reduce conversion even when delivery succeeds.
- Links
- Images
- Compatibility
Team use cases
How engineering, QA, and operations teams use MailSlurp
SRE and platform teams
Load test email-dependent user journeys
Validate that critical workflows keep working when traffic spikes or infrastructure changes roll out.
- Test signup and password reset flows under load
- Detect missing emails and latency regressions
- Turn failures into actionable reliability work
QA teams
Stress test notification and onboarding systems
Use disposable inboxes to validate that your system sends and receives emails reliably at scale.
- Run automated test runs with isolated inboxes
- Validate receipt and content signals
- Reduce flakey tests by using deterministic waits
Engineering managers
Prove readiness before launches
Use load tests with real inboxes to catch reliability issues before releases and high-traffic events.
- Prevent launch-day regressions
- Validate end-to-end workflow reliability
- Share evidence and reports with stakeholders
Getting started
Get this working quickly, then build on it
Day 1
Add one inbox to a load test flow
Start with a small run that provisions an inbox and waits for a matching email.
- Create an inbox as part of the test setup
- Trigger a workflow that sends an email
- Wait for a matching message and record latency
Week 1
Scale to cohorts and record failure patterns
Increase virtual users and validate that expected receipt counts and latency remain stable.
- Create inbox cohorts per run or per virtual user
- Track missing messages and timeouts
- Export results and open remediation tasks
Week 2+
Operationalize with gates and audits
Use load tests as part of release readiness and pair with rendering and deliverability workflows.
- Define pass/fail thresholds for receipt and latency
- Run deliverability cohort checks for bulk workflows
- Add rendering checks for conversion-critical templates
Team fit
How different teams get value
SRE teams
Challenge: Email-dependent workflows can fail under load with no early warning.
What improves: Use real inboxes to validate reliability under load and prevent incidents.
QA teams
Challenge: Load tests often skip inbox validation, leaving blind spots in end-to-end flows.
What improves: Add deterministic inbox waits and assertions to load test suites.
Engineering leaders
Challenge: Launches can regress messaging workflows during high-traffic events.
What improves: Prove readiness with evidence from load tests and audits.
Customer outcomes
What gets better once MailSlurp is in place
Better coverage
Validate real inbox behavior in load tests instead of assuming send success equals delivery success.
Faster detection
Spot missing emails and latency regressions before incidents and launches.
Automation-first
Use APIs and deterministic wait patterns in any load testing framework.
Conversion protection
Pair load tests with audits to prevent broken CTAs and template defects.
Ready to try this with your own workflow?
FAQ
Questions people ask before they start
Does this replace load testing my own infrastructure?
No. Use MailSlurp to validate inbox outcomes inside your load tests. You should still load test your own sending and infrastructure systems as part of end-to-end readiness.
Which frameworks work best?
Any framework that can call HTTP APIs works. Teams commonly use K6, JMeter, Locust, and custom test harnesses.
How do we avoid excessive API calls during load tests?
Use bulk operations where available, avoid tight polling loops, and design tests to batch requests and rely on deterministic waits where possible.
Can we combine load testing with deliverability checks?
Yes. Pair your load runs with deliverability cohort checks to prove receipt outcomes at scale.