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Thread: Setting up an email server -- impossible?

  1. #1
    Join Date
    Jun 2008
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    Uppsala, Sweden
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    30
    Distro
    Ubuntu 9.04 Jaunty Jackalope

    Setting up an email server -- impossible?

    So I've been trying to set up a combined postfix / dovecot server for receiving and sending mails, mostly following this guide:

    http://superuser.com/questions/60552...p-email-server

    I've now managed to get most things working including ssl/tsl. However, I'm still not able to receive emails at all. Also I cannot send email out of the server if I do not specify a relayhost (in that case it works perfectly). I can send emails using telnet both from within the server, and from within the local network. However, I cannot access it from outside the network.

    Here is where I'm confused. I can ssh into the server from outside the network, so it certainly is accessible, even on a custom ssh port. Also, I can telnet into port 25 from within the local network. And if i do an nmap from within the network, ports 25 and 465 are open. However, from outside the local network, all ports are listed as 'filtered', except for port 22 which is 'closed' and my custom ssh port which is 'open'. What does it mean for a port to be filtered, and how can I determine the reason for this, and possibly fix it? Finally, am I trying to do something which cannot be done -- is it impossible to have different email providers, such as google, etc, deliver mail directly to my server?

  2. #2
    Join Date
    Nov 2008
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    Metro Boston
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    12,195
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    Kubuntu 14.04 Trusty Tahr

    Re: Setting up an email server -- impossible?

    Your ISP may block inbound port 25. Most residential Internet accounts ban servers, and some ISPs enforce the rule by blocking inbound traffic. You'll need to read your Terms of Service and talk to them to see if this is the case for you.
    If you ask for help, please have the courtesy to check for responses and thank the people who helped you.

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  3. #3
    Join Date
    Jun 2008
    Location
    Uppsala, Sweden
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    30
    Distro
    Ubuntu 9.04 Jaunty Jackalope

    Re: Setting up an email server -- impossible?

    The server is at my work network, for which the ISP seems to be SUNET -- the swedish univeristy network. I honestly don't know what their policy is on this matter. I'll look into this.

    Anyway, is it true that with port 25 blocked, it will be impossible to have mail delivered to it? What about the other ports, 465 and 578? As I said above, connecting by SSH on many different ports works. Here is probably where I'm confused.

  4. #4
    Join Date
    Mar 2008
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    115

    Re: Setting up an email server -- impossible?

    Quote Originally Posted by ljungkvist View Post
    The server is at my work network, for which the ISP seems to be SUNET -- the swedish univeristy network. I honestly don't know what their policy is on this matter. I'll look into this.

    Anyway, is it true that with port 25 blocked, it will be impossible to have mail delivered to it? What about the other ports, 465 and 578? As I said above, connecting by SSH on many different ports works. Here is probably where I'm confused.
    If a port is blocked then you can't communicate with it. One possible solution is to ask your ISP to release block on port 25.
    Being a target means being on the internet. End of line.
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  5. #5
    Join Date
    Nov 2012
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    265
    Distro
    Ubuntu 13.04 Raring Ringtail

    Re: Setting up an email server -- impossible?

    Did you setup a MX record for your domain?

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