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Monday, November 19, 2012, 16:08

Network Connectivity Diagnostics

Category: General

Solution ID: 00000168

Summary:

How can I diagnose network connectivity problems with PerfectMail?

Answer:

Network problems can be very annoying when they happen. PerfectMail™ provides a number of tools to assist administrators in diagnosing network connectivity issues. Available tools include:

Additionally, PerfectMail performs periodic diagnostics of its configuration and connectivity to local infrastructure and the Internet. PerfectMail displays the health of its DNS configuration, Network Status and Mail Server Status on the Dashboard. The detailed results of these diagnostic tests are available in the Server Status Report (Reports => Server Status).

In e-mail diagnostics, first verify that network connectivity exists then check that DNS resolution is functioning correctly. Following is a step-by-step process to aid in general network diagnostics:

Step 1: Record local settings.

Confirm and record your local network settings under Server Admin => Networking, including: IP Address, Gateway and DNS servers. If you are having problems with a specific mail server, record the IP address of the mail server.

Step 2: Test basic connectivity.

Confirm basic network connectivity using the Ping Tool (Tools => Ping). Ping each device recorded in Step 1 (Gateway Server, each DNS server and any Mail Servers.) Note: Some network devices, including firewalls, may disable ping packet responses or even block the ICMP protocol, used to send ping network packets.

If you are experiencing connectivity issues at this stage, use the TraceRoute Tool (Tools => TraceRoute) to try and identify where the connectivity issue is located. Once again, firewalls and other devices may block the gathering of this information.

This step may identify a problem, or it may simply identify that your firewall is preventing you from gathering this information. If this is your situation, continue the diagnostic process keeping in mind connectivity issues may still be your problem.

Step 3: Confirm DNS resolution.

Confirm DNS resolution is functioning. Use the DNS Lookup Tool (Tools => DNS Lookup) to verify DNS resolution is working. Perform DNS Lookups against each of your listed DNS servers for well known hosts (e.g. www.google.com). Also, perform queries for hosts which will likely note be cached by your DNS server. Confirm DNS responses with those returned by DNS servers external to your organization (e.g. 4.2.2.1, 4.2.2.2, 8.8.8.8, etc.)

Frequently DNS servers may appear to be operating correctly when tests are performed against DNS entries which may be cached, while new DNS queries may fail. (This sometimes happens with Microsoft DNS services; rebooting the service resolves this problem.)

Occasionally, if there has been a significant DNS outage the PerfectMail Mail Transport Service (MTA) may need to be restarted. If you are not receiving incoming e-mail from domains you expect to receive e-mail from, try restarting the MTA service using the following proceedure:

  1. Log in to the PerfectMail web interface;
  2. On the Dashboard, locate the Mail Transport Service (MTA) status at the top left of the screen;
  3. Stop the Mail Transport Service, then start the Mail Transport Service.

Step 4: Confirm SMTP Connections.

If basic connectivity and DNS resolution are functioning correctly, there may be a problem with the actual SMTP exchange. Occasionally, we see problems where firewalls, ISPs, etc. will block SMTP (port 25) traffic. There may also be configuration issues where SMTP services are not running or address acceptance or routing is broken.

You can diagnose SMTP connections using the SMTP Test Tool (Tools => SMTP Test). This tool allows you to specify a mail server IP address and port number, along with sender address, recipient address and simple content for testing purposes. The SMTP Test Tool will actually send an e-mail to the recipient you choose, directly through the specified mail server. During the process of sending this e-mail the actual SMTP commands used during communication will be displayed, along with any error messages.


Tags: mail, server, network, host, connectivity, diagnostics, troubleshooting, tools, procedure

See Also:

Link to this article: http://perfectmail.com/kb/network_connectivity_diagnostics

Updated: Monday, November 19, 2012, 16:08

-- David Rutherford

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Last modified: 2012-11-19, 16:13

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