Hotmail Verification Notices

As you know, there are lots of third party services/software that verify hotmail emails, Our service works well but verification of some small part of email addresses (we will call it “unverifiable address”) are impossible and our service mark it as “valid”. We try to verify these addresses on different verification software and services and  mark it as “valid” too. so It’s issue with all verifiers.

Now more about these “unverifiable addresses”… If you will try to send email letter to “[email protected]” you will get bounce “550 Requested action not taken: mailbox unavailable” during email send process, our service will mark this email as “invalid”.
But if you  try to send email to unverifiable address – your letter will be accepted and all will look like email address really exists, but you will receive bounce letter from “[email protected]” during next two minutes with text:

This is an automatically generated Delivery Status Notification.

Delivery to the following recipients failed.

       [email protected]

That is why it’s an unverifiable address, we have no idea why it’s going through but some little percentage of hotmail emails are “unverifiable addresses”.

Yahoo Verification Notices

All valid emails will be marked as “ok”, all emails that do not exist will be marked as “fail”.
Some valid email addresses are disabled so during mail send you can get some bounces like this:

: host[] said: 554
delivery error: dd Sorry your message to [email protected] cannot be
delivered. This account has been disabled or discontinued [#102]. - (in reply to end of DATA command)

Research over the long term does not give any solution for detecting disable emails without a mail send.
We check  other popular software and services and find that some of them do not verify yahoo at all or have the same problem.