I did several methods to check whether an email address in yahoo is valid or not by using via perl module and also by postfix MTA probing method. In all these methods it tried to sending mails to yahoo only after it says the address is valid or not. Please let me know is there any method to find out the existence of email address in yahoo without sending.

Hi there,

there isn't. Without trying to send an e-mail, all you can do is check an e-mail address for formal correctness. You can take the domain part and run a DNS query on it to find out if the domain exists. You can then take the local part and check if it is up to the rules of RFC 2822. However, there are e-mail providers that allow local parts to violate the specs - GMX, for instance, allows local parts with a trailing dot (like "d.c.m.@gmx.net"), which is against the spec. So a strict validity check would cause occasional false positives.

But once you established that an e-mail address is formally valid, you still cannot check if it really exists other than by trying to send a message to it.

Even then, you can't be sure. A well-configured mail server would indicate immediately in the SMTP dialog that it doesn't accept the message when the recipient is unknown. But many mass hosters don't do it like that - they accept anything and pretend it's okay, and in case of a delivery failure, the sender gets a reply message informing him of the error condition (bounce mail). Some mail servers are even configured not to inform the sender at all. Admins who do that say it's for privacy reasons (though security by obscurity has never been a good strategy).

[X] Doc CPU