Chore: support gmail & yahoo smtp check by api

[OisCircle]

Background

Add support of smtp check by api

What's changed

1. specific host check smtp by api
2. enable gmail & yahoo check by api

[OisCircle]

PR in draft status, waitting to add tests and fix CI.

[OisCircle]

reviewed

[git-hulk]

@OisCircle @lryong I'm not familiar with the email vendor, so not sure if it has any risks in using the signup process to check if the user exists. If yes, I think we should add some comments to notice this. Others are good to me and left one comment inline.

[lryong]

Since it is not practical to check the existence of email addresses through smtp protocol, we have researched that large free email providers such as gmail and yahoo can check email addresses through relevant API interface methods, so we try to add the ability to check the validity of email addresses here.
For more information, please refer to check-if-email-exists/blob/master/core/src/smtp/yahoo.rs

@git-hulk @NeoCN

[git-hulk]

Since it is not practical to check the existence of email addresses through smtp protocol, we have researched that large free email providers such as gmail and yahoo can check email addresses through relevant API interface methods, so we try to add the ability to check the validity of email addresses here. For more information, please refer to check-if-email-exists/blob/master/core/src/smtp/yahoo.rs

@git-hulk @NeoCN

Yes, it sounds good. Need to take care of the risks if plan to use it in production.

[OisCircle]

Since it is not practical to check the existence of email addresses through smtp protocol, we have researched that large free email providers such as gmail and yahoo can check email addresses through relevant API interface methods, so we try to add the ability to check the validity of email addresses here. For more information, please refer to check-if-email-exists/blob/master/core/src/smtp/yahoo.rs

@git-hulk @NeoCN

I have added comments to inform the user about the potential risks and related knowledge on abusing.