Good start, but many mail servers are set not to send confirmations or read receiipts. However you can query the mail server smtp, lookup the mx record.. However many admins turn off vrfy, but you should be able to validate a lot that way.

>Rob gave you a link to validate that the email address looks valid. The only way to test if it is an actual address is to send and email to it and ask for some type of confirmation, either the user clicks a link or sends a reply.
>
>>Look would be enough for my short-term needs. But I guess that "Actually" would be nice later. So I could let the system administrator find out which email adresses are really not good.
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>>Do you have something else to suggest?