port 25 block..

This is a discussion on port 25 block.. within the Networking/Device Communication forums, part of the General Programming Boards category; I got a program that sends email by connecting to a smtp server.. the problem is.. what to do if ...

  1. #1
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    port 25 block..

    I got a program that sends email by connecting to a smtp server..

    the problem is.. what to do if the ISP of the user blocks all but the isp's smtp server??

    there must be a loophole to it.. someway to go around this..

    maybe someway to get the STMP server used by the user on windows registry (without relying on something like outlook, etc..)

    Thanks!!

  2. #2
    * Death to Visual Basic * Devil Panther's Avatar
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    Lightbulb

    connect directly to the dest. user's smtp server then!

    you see, when you send a mail with your isp's local smtp server it gets forwarded to the destination's smtp server.

    example:

    you send to user@hotmail.com
    from me@netvision.net.il

    what happens is you send the mail with your local server: mailgw.netvision.net.il and it forwards it to one of hotmail.com's smtp servers (like mx1.hotmail.com).

    in other words, you can simply send the mail directly to hotmail.com's smtp server!


    goodluck.
    "I don't suffer from insanity but enjoy every minute of it" - Edgar Allen Poe

    http://www.Bloodware.net - Developing free software for the community.

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    fixed some cases.. thanks

    but what if the isp only gives access to their smtp server and none other? :S

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    and the hat of wrongness Salem's Avatar
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    Probably to stop spammers

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    Quote Originally Posted by Salem
    Probably to stop spammers
    Yes.

    So the most ethic solution would be just find the default smtp of a computer.. somewhere in windows' registry or something.. no idea

  6. #6
    * Death to Visual Basic * Devil Panther's Avatar
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    what do you mean by a smtp of a computer???

    and about your isp blocking, well... your isp sucks, they have no right to do so! what are you living in china or something?!
    "I don't suffer from insanity but enjoy every minute of it" - Edgar Allen Poe

    http://www.Bloodware.net - Developing free software for the community.

  7. #7
    and the hat of wrongness Salem's Avatar
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    > the problem is.. what to do if the ISP of the user blocks all but the isp's smtp server??
    If the user can use their normal email client to send email via mail.myisp.com, then any program of yours which also conforms to RFC821 will also be able to send mail via mail.myisp.com
    ALL mail goes via your local gateway, where it is then forwarded to the destination. You DONT connect directly to the destination address in order to send someone email.

    Only incompetent and spam-friendly admins allow unknown persons to connect to mail.randomisp.com from which they can fake all their details and spam anyone they like with near untraceability.

  8. #8
    * Death to Visual Basic * Devil Panther's Avatar
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    but you can act as a smtp server farwarding mail and connect the dest. smtp server yourself and send mail to it's user!
    "I don't suffer from insanity but enjoy every minute of it" - Edgar Allen Poe

    http://www.Bloodware.net - Developing free software for the community.

  9. #9
    Yes, my avatar is stolen anonytmouse's Avatar
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    >> If the user can use their normal email client to send email via mail.myisp.com, then any program of yours which also conforms to RFC821 will also be able to send mail via mail.myisp.com <<

    I think ROCKaMIC is asking how you get the value "mail.myisp.com" without asking the user for it. ROCKaMIC, if you can convince me that you have a valid reason for getting this without asking the user, I can give you some hints. Your talk of a "loophole" doesn't exactly fill me with confidence.

    For further information on why many ISPs block outbound direct email, see search: spam zombie.

  10. #10
    * Death to Visual Basic * Devil Panther's Avatar
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    in other words he's looking for the user's smtp server's address.

    you will need mx dns lookup for this:
    network-tools.com

    check the E-mail Validation, and type the user's e-mail address.
    it will give a list of mx servers, that's the smtp servers for that domain.
    "I don't suffer from insanity but enjoy every minute of it" - Edgar Allen Poe

    http://www.Bloodware.net - Developing free software for the community.

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    Hey 'RockaMic' would you be so kind as to show me your code used to send the email?
    I've tried various ways using winsock, and I've not found a workable solution yet.

    thank you

  12. #12
    * Death to Visual Basic * Devil Panther's Avatar
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    you will need to learn the smtp commands, for a short and simple ref. i suggest: http://www.bsrf.org.uk/tutorials/sendmail.html

    unless your problem is with network programming, because there isn't much to it, you just send these commands to the smtp server.
    "I don't suffer from insanity but enjoy every minute of it" - Edgar Allen Poe

    http://www.Bloodware.net - Developing free software for the community.

  13. #13
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    Here's some code i wrote a while ago that implements the RFC for smtp & MIME:

    SMTP

    Scroll to the end.

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