Free tool online, smtp email validator
This is a free tool to validate an email address with smtp, it contacts mail server and ask for destination recipient and read responses.
It's a free online tool, an email validator built with Minibots, a small PHP class to build spider and web bots.
This email checking tool connects to the mail server and checks whether the email exists. Use this tool freely to check an email address.
Is it possibile to perform SMTP validation on many emails?
As you can see if you try this tool by inserting an email address, it doesn't work properly anymore, because it's hosted on a shared server on a domain which hasn't any email address configured and the majority of the SMTP servers out there consider this configuration not good to send emails and marked the IP of this domain as a possible spammer. There are a lot of sites on the same IP of many differents Aruba clients and maybe some of them is really a spammer.
So, due to spam filters I think that this tecnique to check emails is no longer usable. Since it is too slow: if you have a big database with many emails you will call Gmail servers (for example) a lot of times, from the same IP and this will make Gmail suspect of your good will and will begin to mark you as spammer, or as a bot (which you are).
The best way I've found to check emails and I've tested with my own newsletter software is to specify a proper From header in the email, and make a script that read the specified mailbox regularly to parse returned emails. When an email contains the message that clearly say that the address is not valid I delete the email from the database.