SMTP Connectivity Troubleshooting

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This article will explain methods for troubleshooting connectivity issues with your outbound SMTP mail server. If you are configuring your mailbox for the first time and haven't had any errors, please refer here instead:

Configuring SMTP Server to send email with an outbound mailbox.


What is required for proper SMTP Connectivity with my outbound mail server? needs a clear communication path to send and receive data to and from your SMTP mail server in order to send email. If there is anything hindering that communication, you may receive errors. 

What ports do I need to open on my network?
The required ports would be determined by your mail server and network administrators, so you should consult with them to find the proper settings for your outbound mailbox. Ports 25, 587, or 465 (if using TLS) are the most commonly used ports, and most mail servers have port 25 open by default.

Port 25: If you are using port 25, you should set the Use SSL Setting in the admin set to off
Port 587: If you are using port 587, you could either use SSL or use it without SSL. The Use SSL Setting will be determined by your mail server and network administrators.
Port 465: Port 465 is the SMTPS port. To use port 465, the use SSL setting should be set to On.

Important notes about the SMTP Host field

This field must contain the EXTERNAL hostname of your mail server. (i.e.: and NOT Please verify with your mail server administrator that the hostname that you are using will work externally on your network. If you are using an IP address, it cannot start with 10. (i.e.: or 192. (i.e.: , these are internal IP address ranges.

What are the symptoms of connectivity errors?

  •     Emails being bounced back or unable to be sent.
  •     Emails being stuck in the Outbox.
  •     Customers not receiving their emails
  •     Similar error message to the ones below appearing in your error logs, or on screen in the Admin:

        execution expired

        Last Error: Closed Stream

        Connection Refused

        Timeout Error

        Command received in Invalid state.

What should I do if have any of these issues?

You should run the following email diagnostic tools located on 

MX Lookup: You can check what the outside world (including see's as the MX Record for your domain at using their MX Lookup tool. Type in your domain name ie.: (not the full mail server name) to see what the outside world see's as your mail server name. Verify that the hostname or IP returned is what you are using in

SMTP Diagnostic Tool: This tool mimics sending an email from your mail server, and is located at . Plug your SMTP Host into the field and do an SMTP lookup. Verify that there are no errors.

*** The tool may be limited by relaying, discussed further in the article linked at the bottom of this article.

Port Scan Tool: This tool will validate which ports are open on your mail server, and is located at Plug your SMTP Host into the field and run a port scan. Verify that the port that you are using in the Outbound Mailbox settings in is open. 

Please refer to the article regarding TELNET located here:

If there are issues or anomalies with the MX Record; the SMTP Diagnostic Tool returns any errors;  Port Scan; or TELNET shows that your ports are not open, you should contact your mail or network administrator with this information and determine the next course of action. More than likely a firewall or spam filter has a closed port or is shutting down the connection, and further troubleshooting on your network or mail server would be required to determine the root cause.

I have checked and everything mentioned looks OK, but am still receiving the relay error, now what?
If you feel that you have done everything correctly, and continue to receive errors then you my have missed a device or exception in one of your applications/devices. At this point, it would be highly recommended that you get your email server administrator or network administrators to sniff out the whitelist IPs on your network, and locate the failure point. The servers will try to send email every minute or two, and the connection attempts should be easily visible in your network and mail server logs. While the support team can provide guidance on the potential failure points, the actual configuration is done entirely in you own or your hosting providers network environment.

This article may need to be used in conjunction with the articles below

SMTP Relay Errors:

SMTP Authentication Errors