On Wed, 17 Apr 2002, Jefferson R. Lowrey wrote: > > Did this list ever discuss remote e-mail validation - say in regards to > > sending HTML aware/enabled e-mail with serialized gifs referred back to a DB > > which used the serial number as a key to the e-mail address ? > > > > That way, if someone reads the e-mail you can tell the e-mail was > > 'delivered' ? Maybe follow-up with additional information or something? > > You can't depend on anything in regards to email clients. There is no > guarantee that the particular client will a) accept HTML based email, > b) present the HTML as rendered HTMl, rather than raw text, c) provide > any reliable mechanism for providing notification of email 'receipt'. > > You can't programmatically determine if an email address is valid. > You can't determine in any other manner if an email address is valid, > other than by receiving an email from that address. Even that doesn't > guarantee that the address is *still* valid. It is fully within many > many people's powers to create a new email address for each and every > correspondance they wish to have. It's not very effective, but it is > possible.
If you send an HTML email to [EMAIL PROTECTED] which has IMG tags linking to a cgi URL http://www.bar.com/receipt.cgi?addressee=bob+addressite=foo.com+loadgif=mypicture.gif then your CGI knows [EMAIL PROTECTED] a) accepted the HTML based email, b) presented the email in a fashion that caused the person to load that link, and c) _somebody_ looked at that message, sent to that email address. In my book, that's plenty good enough to say the email address _was_ valid, to some extent. There was a receipt, though I don't who. This assumes, of course, that this trick doesn't get abused by spammers, causing sites to build robots to stuff such a database with bogus addresses. Perhaps you are referring to the converse...if that CGI is not loaded for a given address, it would be hard to know if they didn't receive it, or if they are using a text-based reader like me (eg, Pine, /usr/ucb/mail, etc), or if they've turned off loading pictures because of embarrassing porn spam, or the address is invalid and no one received it. In other words, you may not get a receipt _every_ time someone receives it, but you can get receipts some of the time. For certain groups of people, this may be good enough. -- MattLangford
