Paid services always have some good value and returns. As far as my experience is concerned, you will always have some limited options/features in free services.
As per my opinion, rather than going with free providers, you should consider some valuable email verification provider. Most of the provider will offer you a free trial for the certain period of time. You can test their service and if you are seeing a good result, you can go with their paid plan.
If you are though planning to go with free providers, you can take a look at following:
- Bulk Email Marketing Software
- Simple JSON API for Email Validation
- Free, Powerful Email Validation API
It is important to note that their verification accuracy is not guaranteed. You may not get the results as per your expectations. For the guaranteed delivery and best options, you can consider some best and low cost bulk email verification services providers.
Most of the times, using a paid email valiadation service is way better than using a free option. I would like to recommend you an email validation service that is very affordable, easy to use and GDPR compliant. They detect spam traps, invalid, do not mail, catch-all and abuse emails at competitive prices. The API is available in all plans and offer SDKs for:
•PHP - https://github.com/verifalia/verifalia-php-sdk •Ruby - https://github.com/verifalia/verifalia-ruby-sdk •Node.js - https://github.com/verifalia/verifalia-node-sdk •Java - https://github.com/verifalia/verifalia-java-sdk •.Net. - https://github.com/verifalia/verifalia-csharp-sdk
10K emails are very small, and any of the above vendors can validate them. BTW, are they all business email addresses or they are a mixture of Gmail, Yahoo, AOL, etc....?