Check for existence of mail address

Hi, folks, I'm wondering how to checking existence of a given mail address like foo@bar.com . At 1st I tried: if f (filter_var ($maddr, FILTER_VALIDATE_EMAIL) === false) { /* some sort of error handling code here */ } where $maddr is the address to be checked. But this checks only syntax.. :-( Is there any other function which checks whether this address really exists? And, of course, I want to avoid sending a test mail just for checking :-) Many THX in advance for suggestions, pointers... Rolf -- Dipl.phys. Rudolf Otto Blättner, D 91074 Herzogenaurach, Germany.