Troubleshooting Email problems

Owned by Rakesh
Last updated: Sept 16, 2020
3 min read

Problem

Cannot send outbound emails from NLINK.

If the NLINK Server is configured not to use a separate SMTP server to forward email messages, the NLINK Server itself acts as an SMTP server. NLINK sends email messages directly to the SMTP server(s) for each recipient. NLINK Server's host has to be on domain when NLINK acts as SMTP server.

Each recipient’s email 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 email messages for all of the recipients in that domain. When sending an email 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 email 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, on port 25. Any firewalls in-place between NLINK and the SMTP server must allow NLINK to communicate TCP/IP over port 25.

Common Errors

  1. NLINK cannot reach SMTP Server

    Solution:     Make sure the 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. Alternatively, this may be caused by a firewall configuration that blocks ping commands.

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

  2. Outbound Emails fail with 501 Syntax or other errors.

    Email cannot be sent, get either one of following errors:
    1. Error delivering e-mail message. Unable to communicate with the SMTP server(s). None of the recipients received the message.
      smtpServer.SomeDomain.com: 501 Syntax: HELO hostname
    2. Error delivering e-mail message. Unable to communicate with the SMTP server(s). None of the recipients received the message.
      smtpServer.SomeDomain.com: Command timed out (10060)
    3. Error delivering e-mail message. Unable to communicate with the SMTP server(s). None of the recipients received the message.
      smtpServer.SomeDomain.com:

Solution- Use forwarding SMTP Server.

When NLINK Email Connector is used without a forwarding SMTP server, then NLINK Email acts as SMTP Server. Although not required by SMTP Standard (RFC 2821), as per best practices NLINK will send fully qualified domain name (FQDN) as part of the HELO (or EHLO) command. FQDN is derived based on "Full computer name", and cannot be overwritten. The "Full computer name" can be seen using "Control Panel\System and Security\System".

In case the NLINK host is not part of domain, then sending domain will be blank and emails cannot be sent. Only solution is to use a forwarding SMTP Server.