This is just a PHP class for verify email so if you need to verfiy milions of emails, you should have a good architect (queue)/server to run it.
1. Yes, you can but you have setup queue/node server to check. Let's say you have 1M emails, average time to verify an email is 10 seconds (depends on target server) then you will need 1M x 10 seconds = 10M seconds ~ 2777 hours . But if you have 1000 workers to run parallel, you will only need 2.7 hours. You can use AWS lambda function to scale your worker quickly.
Please note that, you can run this script from command line, each command can be an instance so 1000 workers here may not are 1000 servers. It can be 10 server with 100 tasks run on it
2. Can it work all the times and keep verifying emails on auto mode? => I cannot get your idea but if you want to track an email, you should have a schedule task to verify email
3. Yes, you can see my answer from #1
4. It depends on the target server emailconfiguration.
- If they block all incoming requests for checking email, we cannot determine the email exist or not
- If their server connection is too slow, maybe our script is timeouted (you need increase timeout in script - default is 30 seconds)
5. Currently not support because it's just a PHP class, it's not application
6. It depends on target server speed, average time is about 5-10 seconds per email
7. If it is application issue, I can help. But it is infrastructure, maybe you need supporting from server/hosting provider