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Thread: Telnet, Exchange, and sending of emails in general...

  1. #1

    Question Telnet, Exchange, and sending of emails in general...

    Hi all,

    It's been quite some time since I've worked in the networking, etc. field and I'd love some info' from the more experienced please...

    Here's the situation I'm playing around with:

    We have an Exchange server, but one of our guys sends/recieves his mail through POP, because he is on a different domain with irrelevant (to this discussion) settings.

    I can, using Telnet, connect to his account and send email, but only to accounts on our domains.

    EG: I can send mail through his account to myself, or anyone else in our organization.

    Now, my questions are:

    1. Why can I not send mail externally?

    2. How exactly is this working?

    I know it seems a bit daft, but whilst I can get this to work, I'm not exactly clued up on how it's all working...

    Essentially what I'm trying to prove is that I am able to send email from his account, through the Internet (remember, he's using POP, so he's external - right?), and back to us.


  2. #2


    when you connect via POP you use an SMTP server to inject messages into the server.
    you need to allow him to authenticate on the SMTP server and allow relay for authenticated users

    since he is from an outside domain he cannot relay by default like the users that are local to the machine. you also need to set his client to the " my outgoing server requires authentication" setting.
    the reason you can send messages to local (inside the domain) is the SMTP server accepts and relays messages for its own domain but not for strange ppl (ie outside domains).
    Last edited by Tsimo; 06-08-2009 at 09:51 AM.

  3. #3


    Thanks for the quick reply, Tsimo.

    That does help.

    That said, I should provide a bit more background...

    I'm not looking to change the way he accesses his mail - rather I'm trying to prove him wrong...

    You see, the guy is testing out some software that monitors his email and when I sent mail through his account with Telnet, to myself and other employees, it was not picked up by his monitor...

    Because his mail goes external (POP), his software will usually pick up all mail, whether it be to us, you, or anyone else.

    I don't want to tell him his software is buggy unless I'm sure I'm right.

    The reason I'm hesitant is because I can't send outside of us with Telnet through his account...

  4. #4


    Well that depends on how his program picks up the mail information. if it monitors his Pc`s folders your telnet wont be logged.
    unless he has admin access to the server i dont see how he can monitor it other wise.

    And remember that POP is only the incoming protocol. with only POP you wont be able to send email. you need the SMTP server to send email to anyone.

    To make telnet work you will have to either authenticate your SMTP session via the command line or add your IP to a allow relay form list in the SMTP server settings..

  5. #5
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    Another thing - do not allow SMTP relaying for world+dog - or else your server will be swamped by spammers trying to relay their junk through your email server.

    If you're unsure on what to do, I can redirect you to the most excellent MS Exchange website where they cover every iteration of MS Exchange, together with tutorials.

    And that's where I usually go first when I have problems with Exchange.

    Good luck!
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  6. #6


    Thanks guys,

    I don't have access to the Exchange server, and don't intend changing it. Just trying to get a feel for how the system works. I've never touched Exchange in my life.

    I have established that the guy is solely using his external account to recieve and send. It's stored on an external server, which he then connects to with his mail app', using POP3 and SMTP. It's this server that is monitoring his mail, and to which he can view logs of.

    I have been sending a few test mails through Telnet and I think I've sunk my theory...

    My feeling was that I was able to log in to Telnet and send mail as another user.

    I've just checked the Headers and it seems I was a bit confused - all it seems to be doing is spoofing the 'from' email address.

    It records my IP as the originating IP - which is fine - I understand that.

    How do I 'authenticate' as a user via Telnet?

    Also, what exactly does the EHLO/HELO command do? I can identify myself there as whatever I want?

    Thanks for the help, and the Exchange link.

  7. #7


    Hi. a reference of SMTP Commands can be found here: http://technet.microsoft.com/en-us/l...EXCHG.65).aspx
    you would use the AUTH command if i understand it correctly.



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