Validation Speed

The Bulk Validation

All data is different and the amount of time it takes to process depends on the domains we reach to check whether we need to enable the anti-greylisting technology or not. There are two scenarios:

Antigreylisting is not Enabled

On average, in 2-5 minutes our engines process a list of 10,000 emails (if anti-greylisting is not enabled). This is 1 email per 1 or 2 seconds.


  • 100 emails: ~ 1 minute
  • 1,000 emails: ~ 1 minute
  • 2,500 emails: ~ 1 minute
  • 10,000 emails: ~ 3 minutes
  • 100,000 emails: ~ 30 minutes
  • 200,000 emails: ~ 1 hour

Antigreylisting is Enabled

To behave like a well-configured email sender and create communication with sensitive email servers, sometimes we need to pause between validations. This helps us to reduce the number of unknown statuses. Sometimes, we validate 1 email address 3 times and we need to pause between tries. This method is called anti-greylisting technology. No matter if you have 5 emails or 5000 emails on your list that need anti-greylisting, we need to wait 15~45 minutes.

You can read more about this technique here:

So, this is not a bad thing and it is scalable because you only need to wait for 1-hour maximum – no matter how many emails are on your list (and of course, you will have fewer unknowns).


  • 100 emails: ~ 30 minutes
  • 1,000 emails: ~ 30 minutes
  • 2,500 emails: ~ 30 minutes
  • 10,000 emails: ~ 45 minutes
  • 100,000 emails: ~ 120 minutes
  • 200,000 emails: 2~4 hours

Further Reading

Email validation turnaround time


The validation needs time and the time it takes directly depends on the speed of the email server behind each email. For example, Gmail needs less than 1 second to validate. On the other hand, some servers may take 20 seconds or more. It means we are not limiting the validation speed. The API is built to deliver the validation results as fast as it can. We have set a timeout for the API and it aborts the validation process after 15 seconds and marks the validation results as “Unknown”. You will not pay for “Unknown” validation results.

The antigreylisting technology discussed on the “Bulk validation” section is not applicable to the API.

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