To preserve the operational integrity of the service to all of our customers, there is a maximum concurrency enforced by our systems.


Allowed throughput is 140 email verifications per second.

Throughput exceeding these limits will receive HTTP response code 429 (too many request) for subsequent requests for a duration of one minute.

Suggestions on how to manage throughput

There are several things that it may be helpful to think about to control throughput so as not to exceed the maximum limits described above such as:

  • Test your integration with representative production loads over a period of time. Monitor response codes for any 429’s. If you see any 429’s please reduce the rate at which your application is querying our servers.

  • For applications that can tolerate slight delays in your data processing mesh, consider using queuing infrastructure with a rate controllable processor. Your ‘processor’ can then schedule picking work of of the queue and submitting requests to our systems at a controllable rate.

Large throughput requirements

For sustained throughput more than 50 email verifications per second, please contact us for options on private, dedicated service.