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Email Address Checker

Verifies an Email Address Before You Send
  [vote for,

Don't you hate it when you attach a large file to an email and waste time sending it only to find that your intended recipient has changed their email address {or you mis-typed) and you have to repeat the process?

Why can't an email program like Eudora or Outlook "ping" the account before wasting the ISP's space and your time just to verify that the address you're using is valid?

Sounds like a nice patch that could be sold as a download.

jon3, Aug 12 2003

SMTP protocol - RFC 821 http://www.ietf.org/rfc/rfc0821.txt
Read this to learn how the SMTP protocol works. [danielsf, Oct 04 2004]

SMTP Email Address Validation http://coveryourasp.com/ValidateEmail.asp
Complete with source code. [DrCurry, Oct 04 2004]


       If there were a quick and easy way to do this, it would certainly be abused by spammers, unfortunately.
krelnik, Aug 12 2003

       That's okay. Let them have at it. It's no bother to anyone as the spam would have gone through anyway.
jon3, Aug 12 2003

       Both Eudora and Outlook remember email addresses and have address books, meaning that you are only likely to mispell the address on the first message. You're not protected against people changing their addresses, but slinging out a ping message every time you send an email is a sledgehammer to crack a nut.   

       To keep my email list current, I routinely send out mass emails from one of my vanity sites to everyone in my address book.
DrCurry, Aug 12 2003

       > If there were a quick and easy way...   

       There *is* a quick and easy way to do this. Follow me. Open Telnet on your computer (Open a "Command' or "Terminal" window and type "Telnet"   

       Type: o gateway-r.comcast.net 25   

       When connected, you'll have a conversation like this (the lines beginning with numbers are the server's responses):   

       220 comcast.net - Maillennium ESMTP/MULTIBOX rwcrgxc51 #50   

       helo danserver.starseven.net   

       250 comcast.net   

       mail from:anyaddress123@starseven.ne t   

       250 ok   

       rcpt to:validaddress@comcast.net   

       250 ok   

       rcpt to:invalidaddress@comcast.net   

       551 not our customer ____________________ How this works:   

       1. You look up the MX record for the domain in the e-mail address (here it's gateway-r.comcast.net for @comcast.net), with nslookup.   

       2. You connect to the server given, on port 25 (SMTP).   

       3. Say HELO followed by a domain (most any domain will do)   

       4. Say MAIL FROM:address@address.com (doesn't matter since we're not really going to send a message)   

       5. Say RCPT TO:address@inquestion.com   

       If the address is valid (i.e. there is a mailbox on that server for said address), the server will say "250 ok" If not, then it will say "551..." It will also say 551 if you have the wrong server (for example if you said joe@aol.com to comcast's SMTP-in server).   

       6. Close the connection and report the results to the user.   

       Of course, this is too time- consuming to do _manually_ for each message. But you could write and debug a program in 10 minutes that would do that task in under a second.   

       If this was useful to spammers, they would surely have already implemented it, but why should they care if some address is valid or not? Do you think they put real return addresses on their messages? It's not like they care if they bounce. Any time spent validating addresses is time better spent spamming more.   

       In conclusion, this would be a very simple program extension (or even a quick little standalone applet).
danielsf, Aug 12 2003

       How does it do that before the email is sent kreuner?
custardlove, Aug 13 2003

       I can only get it to inform me if the sending failed (i.e. hotmail tried to deliver the message, but the recipient didn't exist) not do it before the message is sent. Are you sure this is baked kreuner?
custardlove, Aug 13 2003

       The problem is, most wrong addresses do belong to someone. Like telephone numbers.
phundug, Aug 13 2003

       //some SMTP servers may not give you a straight answer about the validity of your RCPT TO: arguments to thwart attempts at harvesting (the more direct VRFY command is often disabled for the same reasons)//
I would say any correctly configured SMTP server would behave that way. I used to work for a major security vendor, and having the VRFY command enabled on your server was considered a vulnerability of your site. (Lets hackers find out account names, so they can then try to break into them). Likewise on returning useful error codes on RCPT TO.
krelnik, Aug 13 2003

       See link for Asp code for this type of email checking. As noted in the article, this only checks for bounced mail.
DrCurry, Aug 13 2003


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