Outgoing SMTP port (25) blocked?

Discussion in 'Tomato Firmware' started by Cal25, Feb 6, 2009.

  1. Cal25

    Cal25 Addicted to LI Member

    My apologies if this has been covered in here or is otherwise obvious. I really tried to search the forums and don't see a good search tool for just the Tomato f/w posts.

    Testing for SMTP access, I get this:

    ~$ telnet fictitious-smtp-server.com 25
    telnet: Unable to connect to remote host: No route to host
    Just to see if the server isn't reachable, I tried this:

    ~$ telnet fictitious-smtp-server.com 80
    Connected to iveylaw.com.
    Escape character is '^]'.
    Connection closed by foreign host.
    So, it seems to be specific to port 25. My laptop has no SMTP troubles outside of my LAN and only the Tomato stands between my laptop and the DSL modem.

    I have extensive QoS set up and have tried to make explicit rules for port 25 to remove any QoS problems I may have caused.

    Tomato: 1.17 (yes, I know, time to upgrade).

    Any ideas where I can look for things that would block port 25 on the Tomato?

    Any help is greatly appreciated.

  2. RonWessels

    RonWessels Network Guru Member

    There are a lot of ISP's that are now blocking port 25 to any machine other than the "official" SMTP server provided by the ISP. This prevents hijacked machines from being effective spam servers.
  3. fyellin

    fyellin LI Guru Member

    I'll second this. I had been hosting some mailing lists on my local machine, all of which suddenly stopped working. A little bit of experimentation showed that Comcast was blocking port 25.
  4. Cal25

    Cal25 Addicted to LI Member

    Thanks. But SMTP from Thunderbird works just fine outside my LAN (i.e., at the local Internet cafe). Same computer inside the LAN, Thunderbird won't send. The 'telnet ... 25' works outside the LAN but not inside. And, it's my server, so I know it's not blocking port 25.

    Any other ideas? Many thanks in advance....

  5. ifican

    ifican Network Guru Member

    so does it work if you take tomato out of the equation, connect your computer directly to your dsl modem. If it works its your router, if it does not then its your isp.
  6. Planiwa

    Planiwa Network Guru Member

    You may find that ping and traceroute have no trouble routing to the host ...

    (Perhaps the correct ICMP error message would have been "Port unreachable".)

    True, but your ISP "stands between your DSL modem and anything it chooses". :)

    As others have said, most ISPs block SMTP to all but their own server.

    Those that don't may find their entire netblock on blacklists.

    Some will open port 25 to customers with static IP addresses that request this.
  7. Cal25

    Cal25 Addicted to LI Member

    SOLVED (Oops, my bad).

    Yes, it was my ISP. I thought by "ISP" ifican meant ISP-supplied mail server. I found the configuration checkbox supplied by my ISP to allow port 25.

    Sorry for the confusion. Many thanks!
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