ME020075 - TRB: Troubleshooting mail client connectivity to MailEnable


Troubleshooting mail client connectivity to MailEnable.


When configuring a mail client to point to the server MailEnable is running on, it should be possible to send and receive a self addressed message.

If the email message cannot be sent, check the error message returned from the email client as it will give an indication of the error. The usual causes for failure to send are:
- the mail client is not configured with the correct SMTP settings to connect to the MailEnable server. Use the IP address of the MailEnable server rather than the host name in order to bypass any DNS related issues with the domain that is being used.
- a firewall (either yours or your ISPs) is preventing access to port 25 on the server. Many ISPs block outbound connections to remote mail servers in order to reduce the amount of spam. Try configuring the SMTP service to also listen on ports 465 and 587 and see if the send then succeeds.
- the MailEnable SMTP service is not running on the server.
- either SPA support or SSL support has been enabled in the mail client settings without having it configured on the server (or the other way around, where the client is trying to send on an SSL port, but the client does not have SSL enabled).

If these items look correct, you can check to see whether the server is contactible from the email client computer. This can be done using the telnet command to see if the server responds. This is described in the article Article ME020207.

If you are able to connect to the server without SSL, but you are unable to connect to an SSL port on the server, make sure that on the server side an SSL certificate has been selected and that an SSL port has been configured. Then restart the server services and check the appropriate Debug log, as this will indicate whether there was any issue configuring the port and using the certificate. You are able to use telnet to connect to the SSL port as a quick check. If it fails to connect then the issue is connectivity to the service (port not available or blocked). If it responds with a readible message then it means the port is not SSL and there is a server configuration change needed. If it connects, but nothing is shown, then it may indicate it is working ok - you would need to use a program such as OpenSSL to connect over SSL to see the actual server response.

If this works, the next thing to try is sending to a domain that is not defined under MailEnable. This will mean that MailEnable's SMTP connector will attempt relay the message. Relaying means that MailEnable is to accept and deliver the message for a domain that is not local. If an immediate error is generated when attempting to do this, then it indicates that the relay settings defined under MailEnable are not compatible with the mail client settings. The most common mistake here is not having enabled SMTP authentication in the mail client. For example, in Microsoft Outlook, this is enabled by ticking the 'My server requires authentication' checkbox.

Finally, if it is possible to send the message, then MailEnable will attempt to process the message and send to its destination. If smart hosting has been enabled under the properties of the SMTP connector, then it will attempt to pass the message to an upstream host. If not, MailEnable will attempt to deliver the message directly to the mail servers representing the target domain. Where smart hosting is used, there must be a trusted connection to the upstream SMTP server. This can be done using IP address ranges i.e. the server will allow the relay if they detect the connection is coming from a trusted location. If their policy does not allow this, then they will deny the relay and a message will inform that the remote host refused to deliver the message.

The best places to determine where messages are going within MailEnable are the Debug and Activity logs. In particular, examine the SMTP logs to determine if and why remote hosts are denying access.


Diagnosing Outlook/Outlook Express Error Codes:Article ME020134

How to configure my mail client when accessing MailEnable via POP and SMTP?:Article ME020198

What are the best relay settings to use?:Article ME020001

Product:MailEnable (All Versions)
Keywords:Mail client connectivity connect email clients connection outlook configuring
Class:TRB: Troubleshooting (Configuration or Environment)
Created:25/02/2003 2:22:00 AM
Revised:Friday, May 20, 2016