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Problem

If NLINK Server is configured not use a separate SMTP server to forward E-mail messages; the NLINK Server itself acts as an SMTP server. NLINK sends E-mail messages directly to the SMTP servers for each recipient.


Each recipient’s E-mail address has a domain, which is the portion of the address after the “@” symbol. Each of these domains has a separate SMTP server that accepts E-mail messages for all of the recipients in that domain. When sending an E-mail message, NLINK must send a copy of the message to a separate SMTP server for each domain used by the recipients.


For each domain used by the recipients of an E-mail message, NLINK must find the address of the SMTP server for that domain. NLINK gets the SMTP servers’ addresses from a Domain Name System (DNS) server.


Once NLINK determines the address for each SMTP server, it communicates directly with each SMTP server using TCP/IP port 25. Any firewalls existing between NLINK and the SMTP server must allow NLINK to communicate over port 25.

Solution

Make sure SMTP Server can be reached by NLINK to send emails. 

  1. Ping the SMTP Server

    Once you have the IP address of the recipient domain’s SMTP server you can now test to see if there is network connectivity between your computer and the SMTP server.
    1. From the command line, run “ping <IP address of SMTP host>”.
    2. Several replies should be received from the SMTP host.If you are unable to ping the SMTP server, there may be a network problem. This may be caused by a firewall configuration.

  2. Send commands to the SMTP Server

    If you have the IP address of the recipient’s SMTP server and you have been able to ping the SMTP server from the NLINK computer you can now test whether you can send commands to and receive responses from the SMTP server.
    1. From the command line, run "telnet".
    2. Enter "open <IP address of SMTP host> 25".
    3. Enter "EHLO <client host name>".
    4. You should see "250 OK" from the SMTP server.
    5. Exit telnet by entering “quit”.
      If you can’t send commands to and receive responses from the SMTP server, it may be because port 25 is blocked by a firewall.
       
  3. Use SMTP to forward emails

    In cases where infrastructure prevents execution of SMTP queries, NLINK will not be able to act as e-mail client. In all such cases, specify SMTP Server to which NLINK will forward all emails to.

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