(reason: 550 Host unknown) sendmail Solaris 10

Posted on 2007-09-29
Last Modified: 2013-12-21
Mail won't get sent. Here's output in /var/mail for the user:
The original message was received at Sat, 29 Sep 2007 11:44:08 -0500 (CDT)
from localhost []

   ----- The following addresses had permanent fatal errors -----
    (reason: 550 Host unknown)

   ----- Transcript of session follows -----
550 5.1.2 <>... Host unknown (Name server: mailhost: host not found)

Content-Type: message/delivery-status

Reporting-MTA: dns; hostxxx
Received-From-MTA: DNS; localhost
Arrival-Date: Sat, 29 Sep 2007 11:44:08 -0500 (CDT)

In my /etc/hosts I have:
10.xx.xx.xx      mailhost mail

I can ping both mail and mailhost. I can manually telnet mailhost  on port 25 and send an email. I verified sendmail is active. I even stopped and started it. I can ping a public host like and it replies.
online         11:38:58 svc:/network/smtp:sendmail

I have all defaults in /etc/mail.

Any ideas?
Question by:jjc_mn
    LVL 38

    Accepted Solution

    Please post your file here.
    Make sure you have
    define(`SMART_HOST', `')
    where is a back quote ` in front of SMART_HOST and smtp-server......

    Author Comment

    Here's my If I make changes do I  only have to stop and start the snedmail service or do I need to do more?

    #  This is a configuration file for SunOS 5.8 (a.k.a. Solaris 8) and later
    #  subsidiary machines.  It has support for local and SMTP mail.  The
    #  confFALLBACK_SMARTHOST macro is enabled, which means that messages will
    #  be sent to that host (which is set to mailhost.$m [$m is the local domain])
    #  if MX records are unavailable.  A short-cut rule is also defined, which
    #  says if the recipient host is in the local domain, send to it directly
    #  instead of the smart host.
    #  If you want to customize this further, copy it to a name appropriate
    #  for your environment and do the modifications there.
    VERSIONID(`@(#)      1.11 (Sun) 06/21/04')
    define(`confFALLBACK_SMARTHOST', `mailhost$?m.$m$.')dnl
    LVL 48

    Assisted Solution

    What does:

    /usr/sbin/host -t mx



    Author Comment

    /usr/sbin/host -t mx mail is handled by 10

    Author Comment

    This might have an affect. I added a second Ethernet card the other day. and added the 63.xx.xx.xx route. I rebooted after so either the new route or a reboot may have stopped sendmail. Sendmail used to work.

    Routing Table: IPv4
      Destination           Gateway           Flags  Ref   Use   Interface
    -------------------- -------------------- ----- ----- ------ ---------
    63.xx.xx.xx          111.xx.xx.x        UGH         1    125  
    10.xx.xx.xx          10.xx.xx.xx          U         1    170  ce0
    xx.xx.0.0            xx.xx.xx.xx          U         1    500  ce1            10.xx.xx.xx          U         1      0  ce0
    default              10.xx.xx.xx          UG        1   1832              UH       33 682283  lo0

    Author Comment

    turned out the domain name was removed from the host entry
    I.E. was:
    10.xx.x.xx    hostname
    and it needed to be
    10.xx.x.xx    hostname

    did that, restarted sendmail and all works

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