The Remote Certificate is Invalid

Configuring the SMTP settings on a DotNetNuke website gave the error, remote certificate is invalid, from the mail server:

There has been an error trying to send the test email. The error is:
The remote certificate is invalid according to the validation procedure

I often find that errors on a DotNetNuke website are logged with further information in the Event Log. To view this navigate to Admin/Event Viewer, from the top navigation bar.

Dependant upon how many messages are created on your website, for example users logging in, the error message which you are looking for may be on the second or third page. If necessary take a note of the time and force the error again, to get it on the first page.

In the Event Viewer log the gist of the error message was:

There has been an error trying to send the test email. The error is:
The message was not delivered to the following address(es) –

I found error relay not permitted.

Where the SMTP host settings for the DotNetNuke installation is configured to use a defined mailbox if choosing to use a secure connection the domain name of the certificate and mail account needs to be the same domain as that configured in the settings.

The error may be resolved by either using a mailbox with the correct domain certificate. or by using an unsecured mailbox and unticking the SSL option.