If you want to know if an email address is valid, you connect to gmail's server ...

parhamn · on Dec 13, 2013

Are you sure about this? Just tested it out:

    openssl s_client -connect  smtp.gmail.com:465 -crlf

    220 mx.google.com ESMTP u17sm2709629qeb.4 - gsmtp
    helo
    250 mx.google.com at your service
    auth login
    334 VXNlcm5hbWU6
    < BASE_64 USERNAME> 
    334 UGFzc3dvcmQ6
    < BASE_64 PASSWORD> 
    235 2.7.0 Accepted
    MAIL FROM: <my_email>
    250 2.1.0 OK u17sm2709629qeb.4 - gsmtp
    rcpt to: <my_email>
    250 2.1.5 OK u17sm2709629qeb.4 - gsmtp
    rcpt to: <emaildne39g39jd9j9jfsdk@gmail.com>
    250 2.1.5 OK u17sm2709629qeb.4 - gsmtp

I get an OK with BS emails too...

tedunangst · on Dec 13, 2013

You should try telnet to port 25 and don't login. If you're sending what could be an outgoing email, it is more likely to queue it.

    MAIL FROM:<tedu@tedunangst.com>
    250 2.1.0 OK g15si484689qej.92 - gsmtp
    RCPT TO:<tedunangst1233141@gmail.com>
    550-5.1.1 The email account that you tried to reach does not exist. Please try
    550-5.1.1 double-checking the recipient's email address for typos or
    550-5.1.1 unnecessary spaces. Learn more at
    550 5.1.1 http://support.google.com/mail/bin/answer.py?answer=6596 g15si484689qej.92 - gsmtp

parhamn · on Dec 13, 2013

Cool, thanks!

dspillett · on Dec 13, 2013

That will only tell you if the account exists. The request for an image tells you more: that that account is actually used.