Re: Mail delivery wierdness

From: Ryan Thompson (ryan_at_sasknow.com)
Date: 07/22/03

  • Next message: Thanjee Neefam: "fd0 device errors" 
    Date: Mon, 21 Jul 2003 19:23:59 -0600 (CST)
To: keith@smmc.qld.edu.au

    keith@smmc.qld.edu.au wrote to Free bsd :

    > Hi all,
    > I am trying to connect to an exchange server via my new gateway ipfilter
    > fbsd 4.7 ipnat firewall.
    > Telnetting to the server inside to port 25 reveals...
    >
    > Connected to 203.44.yyy.xx
    > Escape character is ']'.
    > Connection closed by foreign host.
    >
    > Why would it close instantly?

    That's usually the behaviour indicating that there is a server at
    203.44.yyy.xx, but there is no service listening on port 25. (Or, maybe
    your fancy ipfilter firewall is simulating the equivalent).

    The first thing you should do is confirm that the server in question
    *is* actually listening on port 25. MS Exchange is pretty far beyond the
    charter of this list, but general network techniques would still apply:

    Try the same telnet test using the win32 telnet on the server itself.
    (i.e., telnet localhost:25, and try it by the public IP in case Exchange
    isn't listening on localhost for some reason). If it won't talk SMTP
    with you in either case, you won't get any farther. On the other hand,
    if the test is successful, try the same thing from the next hop (your
    FreeBSD gateway?).

    If you isolate the problem to the gateway (and/or every host directly
    connected to the other side of your gateway), you'd probably do well to
    forward your firewall rules and ipnat config to the list (as well as a
    description of what you're trying to accomplish with your config), in
    which case we'll be able to give you better specific instructions.

    > Does this reveal while I can't send mail to any email account on it?
    > Is this an exchange hassle? Is port 25 to be only tcp or udp as well.

    SMTP is a connection-oriented service. SMTP can, in theory, be used
    over transport layers other than TCP, but SMTP over UDP would require a
    fair hack to SMTP to implement. So, the short answer is, forget about
    UDP. :-)

    - Ryan 

    -- 
  Ryan Thompson <ryan@sasknow.com>
  SaskNow Technologies - http://www.sasknow.com
  901-1st Avenue North - Saskatoon, SK - S7K 1Y4
        Tel: 306-664-3600   Fax: 306-244-7037   Saskatoon
  Toll-Free: 877-727-5669     (877-SASKNOW)     North America
_______________________________________________
freebsd-questions@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-questions
To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org"
  • Next message: Thanjee Neefam: "fd0 device errors"

    Relevant Pages

    • [NT] Vulnerability in Exchange Server Could Allow Arbitrary Code Execution (MS03-046)
      ... Get your security news from a reliable source. ... In Exchange Server 5.5, a security vulnerability exists in the Internet ... an unauthenticated attacker to connect to the SMTP port on an Exchange ...
      (Securiteam)
    • RE: SMTP error (only from Outlook)
      ... This issue appeared on specify user or all SMTP clients? ... If yes, in Exchange System ... Is there any local bridgehead server listed in "Local ... to over three dozen open relay block lists. ...
      (microsoft.public.windows.server.sbs)
    • RE: strange email errors
      ... you to check the relay configuration on the SBS server. ... please restart the SMTP virtue server and Exchange ... Please also refer to the following steps to create a new SMTP Connector to ...
      (microsoft.public.windows.server.sbs)
    • Re: Exchange issues
      ... Are you up to date on all your Service Packs, both Windows and Exchange? ... > all traffic on port 25 to the SBS Exhange server. ... I suspected SMTP relaying becuase ... > You should verify that the server really isn't an open relay: ...
      (microsoft.public.exchange2000.admin)
    • Filtering email on ISA
      ... Unless you choose to create a new IIS SMTP Virtual ... Server, ordinarily you will want to Server Publish ... directly to the Exchange SMTP, ...
      (microsoft.public.isa)
    Loading